Here we have the final example in the text of an original Hebrew-like if-and construction. Such constructions are, of course, ungrammatical in English; thus the and was removed in the 1837 edition. We have already noted many examples of this kind of construction elsewhere in the text. For another example involving an if- clause, see nearby under Ether 14:1. For a general discussion, see under hebraisms in volume 3.
Summary: Restore in Moroni 10:4 the original Hebraistic and that separated the if- clause from its following main clause; such usage was fairly common in the original text of the Book of Mormon.