Here a completely unnecessary in was accidentally inserted in the 1852 LDS edition, probably by the compositor. The error is obvious, and it was therefore removed in the following LDS edition (1879). Perhaps the source of the extra in was the frequent use of the word inhabitants in the larger passage (nine times in verses 3–10). Yet for each instance of “the city (of ) X … and the inhabitants thereof ”, there is no in immediately preceding “the city (of ) X”.
Summary: Maintain in 3 Nephi 9:7 (and elsewhere in 3 Nephi 9:3–10) the systematic expression “the city (of ) X … and the inhabitants thereof ”—that is, without any in immediately preceding “the city (of ) X”.