First of all we are told that King Mosiah has some interpreters which can be used to translate the 24 plates that the people of King Limhi found:
Mosiah 8
7 And the king said unto him: Being grieved for the afflictions of my people, I caused that aforty and three of my people should take a journey into the wilderness, that thereby they might find the land of Zarahemla, that we might appeal unto our brethren to deliver us out of bondage.
8 And they were lost in the wilderness for the space of amany days, yet they were diligent, and found not the land of Zarahemla but returned to this land, having traveled in a land among many waters, having discovered a land which was covered with bbones of men, and of beasts, and was also covered with ruins of buildings of every kind, having discovered a land which had been peopled with a people who were as numerous as the hosts of Israel.
9 And for a testimony that the things that they had said are true they have brought atwenty-four plates which are filled with engravings, and they are of pure gold.
10 And behold, also, they have brought abreastplates, which are large, and they are of bbrass and of copper, and are perfectly sound.
11 And again, they have brought swords, the hilts thereof have perished, and the blades thereof were cankered with rust; and there is no one in the land that is able to interpret the language or the engravings that are on the plates. Therefore I said unto thee: Canst thou translate?
12 And I say unto thee again: Knowest thou of any one that can translate? For I am desirous that these records should be translated into our language; for, perhaps, they will give us a knowledge of a remnant of the people who have been destroyed, from whence these records came; or, perhaps, they will give us a knowledge of this very people who have been destroyed; and I am desirous to know the cause of their destruction.
13 Now Ammon said unto him: I can assuredly tell thee, O king, of a man that can translate the records; for he has wherewith that he can look, and translate all records that are of ancient date; and it is a gift from God. And the things are called interpreters, and no man can look in them except he be commanded, lest he should look for that he ought not and he should perish. And whosoever is commanded to look in them, the same is called seer.
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19 And now, when Ammon had made an end of speaking these words the king rejoiced exceedingly, and gave thanks to God, saying: Doubtless a agreat mystery is contained within these plates, and these interpreters were doubtless prepared for the purpose of unfolding all such mysteries to the children of men.
And just to make sure we didn't miss that...
Mosiah 21
25 Now king Limhi had sent, previous to the coming of Ammon, a asmall number of men to bsearch for the land of Zarahemla; but they could not find it, and they were lost in the wilderness.
26 Nevertheless, they did find a land which had been peopled; yea, a land which was covered with dry abones; yea, a land which had been peopled and which had been destroyed; and they, having supposed it to be the land of Zarahemla, returned to the land of Nephi, having arrived in the borders of the land not many days before the bcoming of Ammon.
27 And they brought a arecord with them, even a record of the people whose bones they had found; and it was engraven on plates of ore.
28 And now Limhi was again filled with joy on learning from the mouth of Ammon that king Mosiah had a agift from God, whereby he could binterpret such engravings; yea, and Ammon also did rejoice.
And sure enough, Mosiah translates the 24 Jaredite plates with his interpreters:
Mosiah 28
11 Therefore he took the records which were engraven on the plates of abrass, and also the plates of bNephi, and all the things which he had kept and preserved according to the commandments of God, after having translated and caused to be written the records which were on the cplates of gold which had been found by the people of Limhi, which were delivered to him by the hand of Limhi;
12 And this he did because of the great anxiety of his people; for they were desirous beyond measure to know concerning those people awho had been destroyed.
13 And now he translated them by the means of those two astones which were fastened into the two rims of a bow.
14 Now these things were prepared from the beginning, and were handed down from generation to generation, for the purpose of interpreting languages;
15 And they have been kept and preserved by the hand of the Lord, that he should discover to every creature who should possess the land the iniquities and abominations of his people;
16 And whosoever has these things is called aseer, after the manner of old times.
17 Now after Mosiah had finished atranslating these brecords, behold, it gave an account of the people who were cdestroyed, from the time that they were destroyed back to the building of the dgreat tower, at the time the Lord econfounded the language of the people and they were scattered abroad upon the face of all the earth, yea, and even from that time back until the creation of Adam.
18 Now this account did cause the people of Mosiah to mourn exceedingly, yea, they were filled with sorrow; nevertheless it gave them much knowledge, in the which they did rejoice.
19 And this account shall be awritten hereafter; for behold, it is expedient that all people should know the things which are written in this account.
20 And now, as I said unto you, that after king Mosiah had done these things, he took the plates of brass, and all the things which he had kept, and conferred them upon Alma, who was the son of Alma; yea, all the records, and also the interpreters, and conferred them upon him, and commanded him that he should keep and preserve them, and also keep a record of the people, handing them down from one generation to another, even as they had been handed down from the time that Lehi left Jerusalem.
But, hang on a minute, didn't God give the interpreters to the Brother of Jared to keep with the plates?:
Ether 3
21 And it came to pass that the Lord said unto the brother of Jared: Behold, thou shalt not suffer these things which ye have seen and heard to go forth unto the world, until the time cometh that I shall glorify my name in the flesh; wherefore, ye shall treasure up the things which ye have seen and heard, and show it to no man.
22 And behold, when ye shall come unto me, ye shall write them and shall seal them up, that no one can interpret them; for ye shall write them in a language that they cannot be read.
23 And behold, these two stones will I give unto thee, and ye shall seal them up also with the things which ye shall write.
24 For behold, the language which ye shall write I have confounded; wherefore I will cause in my own due time that these stones shall magnify to the eyes of men these things which ye shall write.
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28 And it came to pass that the Lord commanded him that he should seal up the two stones which he had received, and show them not, until the Lord should show them unto the children of men.
So God gave the interpreters to the Brother of Jared and they got sealed up with the plates.
But Mosiah already had the interpreters when the Jaredite plates were discovered, and the interpreters are revealed to have been passed down with the other goodies since Lehi's time.
eh?