Here Joseph Smith accidentally crossed out the and when he crossed out the “it came to pass” phrase in his editing for the 1837 edition. The 1837 edition itself retained the and since some sort of connective element is expected. For a similar example where Joseph Smith initially deleted the and when he crossed out “it came to pass”, see Mosiah 22:9–10. For a general discussion of Joseph’s occasional removal of “it came to pass”, see under come to pass in volume 3. The critical text will restore all original instances of “it came to pass” that have been deleted from the standard text.
Summary: Restore in Mosiah 28:6 the instance of “and it came to pass” that Joseph Smith deleted in his editing for the 1837 edition.