The geography of the Book of Mormon becomes important in the next several verses. The Nephites landed in an unnamed area and remained there until the conflict between Nephi and his brothers became so intense that Nephi had to take as many as would follow him to another area. They were taken to "the land of Nephi." The journey was described as taking many days (2 Nephi 5:7). The Nephites remained here for several centuries.
The next move is being described here in Omni. Apparently Mosiah takes as many as will follow him and travels out of the land of Nephi. Presumably, each Nephite move sends them further north. This is not explicitly recorded but makes sense given the fact that the Lamanites were later described as inhabiting the lands to the south and the Nephites were described as inhabiting the lands to the north. So Mosiah takes his people from the land of Nephi to the land of Zarahemla. Elsewhere in the Book of Mormon, the record indicates that this distance could be traveled in a 21 day journey (see Mosiah 23:3;24:20-25). There is nothing in the record which suggests that great, long journeys over thousands of miles took place among the Nephites. Those who make such claims have little or no evidence for the same.
In general, the geography of the Book of Mormon cannot be accurately determined. Many have attempted to designate certain ancient sites as prominent Nephite cities. These attempts are spurious at best. The individual who claims to have figured out Book of Mormon geography is not honest about what he or she can fairly claim. There just isn't enough information in the Book of Mormon to come to distinct conclusions about the locations of Zarahemla, the site of the last battle, or other Nephite cities.
President Anthony V. Ivins
"There is a great deal of talk about the geography of the Book of Mormon. Where was the land of Zarahemla? Where was the City of Zarahemla? and other geographic matters. It does not make any difference to us. There has never been anything yet set forth that definitely settles that question. So the Church says we are just waiting until we discover the truth. All kinds of theories have been advanced. I have talked with at least half a dozen men that have found the very place where the City of Zarahemla stood, and notwithstanding the fact that they profess to be Book of Mormon students, they vary a thousand miles apart in the places they have located. We do not offer any definite solution. As you study the Book of Mormon keep these things in mind and do not make definite statements concerning things that have not been proven in advance to be true." (Conference Reports, Apr. 1929, p. 16)
Harold B. Lee
"Don't be concerned over Book of Mormon geography. Some say the Hill Cumorah was in southern Mexico (and someone pushed it down still farther) and not in western New York. Well, if the Lord wanted us to know where it was or where Zarahemla was, He'd have given us latitude and longitude, don't you think? And why bother our heads trying to discover with archaeological certainty the geographical locations of the cities of the Book of Mormon like Zarahemla? (66-07)
"The witness of the Book of Mormon is not found in the ruins of Central and South America. They may be outward evidences of a people long since disappeared. The real witness is that which is found in the Book of Mormon itself." (The Teachings of Harold B. Lee, p. 156)