Alma 62:29

therefore all the prisoners of the Lamanites did join the people of Ammon, and did begin to labor exceedingly, tilling the ground, raising all manner of grain, and flocks, and herds of every kind; and thus were the Nephites relieved from a great burthen; yea, insomuch that they were relieved from all the prisoners of the Lamanites.

All the Lamanite prisoners joined the people of Ammon. They began to work very hard. They worked the ground. They grew all kinds of grain and raised flocks and herds of every kind. The Nephites were relieved from a great load. They were relieved from all the Lamanite prisoners.

So all the Lamanite prisoners joined the people of Ammon and began working hard—plowing the ground, raising grain, and tending flocks and herds. This lifted a great burden from the Nephites, freeing them from having to guard all those prisoners.