Oliver Cowdery initially wrote “now it came to pass” in the printer’s manuscript; then somewhat later he crossed out the now and supralinearly wrote an ampersand. The ink flow for the ampersand is considerably broader, which implies that Oliver made the correction later with a duller quill, probably when he proofed 𝓟 against 𝓞. This change undoubtedly represents the reading of the original manuscript, especially since there are numerous examples of both “now it came to pass” and “and it came to pass” (as well as “and now it came to pass”) in the Book of Mormon text; there would have been no grammatical motivation for Oliver Cowdery to edit “now it came to pass” to “and it came to pass”. For each case of “it came to pass”, the critical text will follow the earliest extant reading for the initial connector, thus “and it came to pass” here in Helaman 8:7.
Summary: Accept in Helaman 8:7 the corrected reading in 𝓟 with the sentence-initial and as the reading of the original text (“and it came to pass”).