Complex sentence: Smith published what he said was a translation of these plates in March 1830 as the "Book of Mormon", named after Mormon, the ancient prophet-historian who compiled the book, and on April 6,1830, Smith founded the Church of Christ.
Split into simpler sentences: Smith published what he said was a translation of these plates in March 1830 as the Book of Mormon, named after Mormon, the ancient prophet--historian who compiled the book. On April 6,1830, Smith founded the Church of Christ.