Mosiah 1:1 - 1:5

Mosiah 1:1 And now there was no more contention in all the land of Zarahemla, among all the people who belonged to king Benjamin, so that king Benjamin had continual peace all the remainder of his days.

Peace was finally established in the land of Zarahemla. The people dealt with each other as Christians should. As a result, there were no contentions for the remainder of king Benjamin’s reign.

Mosiah 1:2 And it came to pass that he had three sons; and he called their names Mosiah, and Helorum, and Helaman. And he caused that they should be taught in all the language of his fathers, that thereby they might become men of understanding; and that they might know concerning the prophecies which had been spoken by the mouths of their fathers, which were delivered them by the hand of the Lord.

King Benjamin had three sons named Mosiah, Helorum and Helaman. He made sure they were educated as to be able to read and write in the language that was used on the plates. His desire was that his sons would become men of understanding by being able to read and study the history of the Nephites and even more important that they would be familiar with the revelations and the words of the prophets.

Mosiah 1:3 And he also taught them concerning the records which were engraven on the plates of brass, saying: My sons, I would that ye should remember that were it not for these plates, which contain these records and these commandments, we must have suffered in ignorance, even at this present time, not knowing the mysteries of God.

King Benjamin impresses on his sons the importance of possessing the brass plates that contain the history of the house of Israel and the commandments given to them from God. If they did not have these records, they would be in total ignorance of how they should live their lives and conduct their affairs with each other. And even more so, not knowing how God deals with his children here on earth.
[If we did not have these records in our day we would be like the primitive peoples that are in various parts of the earth. We would have no knowledge of our past, what codes we should be living other than what we invent and what our potential is in the life to come if we have such a concept.]

Mosiah 1:4 For it were not possible that our father, Lehi, could have remembered all these things, to have taught them to his children, except it were for the help of these plates; for he having been taught in the language of the Egyptians therefore he could read these engravings, and teach them to his children, that thereby they could teach them to their children, and so fulfilling the commandments of God, even down to this present time.

One must have the scriptures in their possession to keep a true knowledge of what they teach. Their teachings and stories cannot be remembered in their completeness or passed down orally without undergoing change over time as all oral traditions do. Lehi made sure that the language that was used to keep the records which was Egyptian was taught to his children and they in turned passed this knowledge down to their children until this time of king Benjamin as the Lord had commanded them

Mosiah 1:5 I say unto you, my sons, were it not for these things, which have been kept and preserved by the hand of God, that we might read and understand of his mysteries, and have his commandments always before our eyes, that even our fathers would have dwindled in unbelief, and we should have been like unto our brethren, the Lamanites, who know nothing concerning these things, or even do not believe them when they are taught them, because of the traditions of their fathers, which are not correct.

Mormon relates that if they did not have the plates, the Nephites would have become like the Lamanites who were totally ignorant of the commandments and would only be living according to their traditions of their ancestors. And since their traditions miss represented their past history with the Nephites, it was the source of all the troubles between the two groups.
[Having records is one of the measures of civilization. Those who have little or no written records that are available to the general population are controlled by tradition and the strong arm of ambitious leaders with cohorts to back them up. They are usually savage in their treatment of each other and others who are of their own people. The tribal society seems to be the norm without records.]