bàtaichean is the plural ie boats. bàta/bhàta is singular boat
But watch out because in Gaelic 1 & 2 are singular, so 1 boat, 2 boat, 3 boats...
Also if you were asking "how many boats?" in Gaelic you would use the singular "how many boat?" or "cia mheud bàta?"
Hope that helps and if anyone thinks I'm not correct pleast let me know - still just a learner.