The 1892 RLDS edition accidentally inserted the preposition of here, thus changing “the land Shilom” to “the land of Shilom”. Normally, the text refers to either “the land of Shilom” (ten times) or “the city of Shilom” (two times), but there is one other occurrence of “the land Shilom”—in fact, later on in this same verse (which the 1892 edition did not change to “the land of Shilom”):
As discussed under 1 Nephi 17:7, the Book of Mormon text allows variation with respect to the use of of in the phrases “the land (of) X” and “the city (of) X”. In each case, we allow the earliest textual sources to determine the reading. Thus here in Mosiah 11:13, we maintain the phraseology “the land Shilom”—that is, without the of.
Summary: Maintain the two occurrences of “the land Shilom” in Mosiah 11:13; although “the land of Shilom” is more common, its occurrence without the of in Mosiah 11:13 appears to be intended.