As discussed nearby under Alma 47:1, into is the preferred preposition when dealing with movement across geographical boundaries. Just as in Alma 47:1, the 1837 edition is responsible for the change to in. The 1920 LDS edition restored the original into here in Alma 47:29 but not in Alma 47:1. On the other hand, the 1908 RLDS edition restored the into in Alma 47:1 but not here in Alma 47:29. Elsewhere, in expressions of the form “come over in(to) a land”, the preposition is consistently into (eight times). For a list of examples where into has been replaced by in, see under Mosiah 23:26.
Summary: Maintain in Alma 47:29 the preposition into, the reading of the earliest textual sources (“they … came over into the land of Zarahemla”).