"Girls drink milk."
Translation:Meisjes drinken melk.
Good guess, but actually -en and -s are two different plural suffixes, used for different nouns. English has both of these plural endings as well, for example in oxen (ox + en) and horses (horse +s). So "meisjen" (meisje + en) is incorrect but meiden is correct (meid + en). There are rules you look up to determine which ending a noun should take.