As explained under 3 Nephi 10:2, the 1830 typesetter tended to replace kindreds with kindred. Here in 3 Nephi 28:29, he apparently made this mistake. Elsewhere in the Book of Mormon, we always have agreement in number for the conjuncts nation(s), kindred(s), and tongue(s)—although the final conjunct, people, is always in the singular. Ignoring this singular people, we get all plurals nine times and all singulars eight times; thus the 1830 reading here in 3 Nephi 28:29 is very likely the result of the 1830 typesetter’s preference for the singular kindred. The subsequent edition (1837) restored the expected plural, kindreds.
Summary: Maintain in 3 Nephi 28:29 the expected agreement in number when nation(s), kindred(s), and tongue(s) are conjoined.