We do not have to prove the Book of Mormon is true. The book is its own proof. All we need to do is read it and declare it! The Book of Mormon is not on trial—the people of the world, including the members of the Church, are on trial as to what they will do with this second witness for Christ.
I testify that the Book of Mormon is the word of God; and therefore Jesus is the Christ, Joseph Smith is a prophet, The Church of Jesus Christ of Latter-day Saints is true, with its authorized servants to perform the ordinances of salvation today, in the name of Jesus Christ, amen. (“A New Witness for Christ,” Ensign, Nov. 1984.)