No, that sentence does not make sense.
Imagine you are talking about your collection of jeans. You can say "j'en ai un noir" (I have a black one). In plural: "j'en ai des noirs". (In French, "a pair of jeans" = un jean).
Now for feminine words, like "chemise" (shirt): "j'en ai une noire" for singular and "j'en ai des noires" for plural.
Duolingo never gives any explanation about grammar and syntax.
When you discover a new word or construction:
either you guess (in this case, that according to singular/plural and masculine/feminine words, there are several forms for the same adjective: noir (masc. sing.), noire (fem. sing.), noirs (masc. plur.) and noires (fem. plur.).)
or you go to the main "Discussion" page and use the Search feature to check whether somebody else has asked a similar question (which is the case at 99%) and you read the answers already given by other learners.