Here the 1830 typesetter accidentally replaced the plural plunderings with the singular plundering,
even though the conjoined nouns are in the plural. Elsewhere the text is
consistent in using the singular plundering when immediately conjoined nouns are singular, but the plural plunderings when those nouns are plural:
conjoined with singular nouns
conjoined with plural nouns
In the last example, Oliver Cowdery initially wrote plundering in 𝓟, but this was the last word on the page and he simply ran out of space at the end of the line. Oliver never actually finished writing the word since the i was not dotted. He simply crossed out plundering and then wrote the full plural form as the first word at the beginning of the next page of 𝓟.
Thus the original text in Helaman 3:14 is consistent with other usage, especially in the second half of the Book of Mormon (where only the plural plunderings is found). Here in Helaman 3:14, the critical text will restore the plural for this noun.
Summary: In accord with the reading of the manuscripts, restore the plural plunderings in Helaman 3:14 (which is consistent with other usage in the text).