The question here in this summarizing statement is whether which refers to the cities or the Lamanites. In his editing of 𝓟 for the 1837 edition, Joseph Smith emended the which to who, which means that at that time he interpreted the which as referring to the Lamanites. The previous listing of the converted peoples in this chapter supports this interpretation, namely, that the text is referring to the peoples who have been converted rather than to the cities:
But Joseph’s emendation in verse 13, changing which to who, never showed up in the 1837 edition; instead, the original which was retained.
The question, then, is whether the Book of Mormon text allows cities to be converted. Or can only people be converted? Elsewhere in the text, there are no references to the conversion of cities, although such language would be unremarkable in today’s English. In the Book of Mormon, only people are converted. In fact, two verses later in this chapter the text makes it clear that it was the people in the cities who were converted:
Here in which refers to the cities while they refers to the Lamanites.
All of these examples in verses 8–12 and 15, plus all the others in the Book of Mormon, argue that Joseph Smith’s interpretation of which here in Alma 23:13 was indeed correct; that is, which refers to the Lamanites, not to the cities. Of course, in the critical text, we do not need to determine the referent for which; here the critical text will simply maintain the which of the original text. For further discussion, see under which in volume 3.
Summary: Retain the original relative pronoun which in Alma 23:13: “and these are the names of the cities of the Lamanites which were converted unto the Lord”; internal evidence argues that which here refers to the Lamanites, not to the cities.