"They need other artists."

Translation: One potrzebują innych artystów.

[pie3636]

Is there any rule to know which nouns end in -ów in the genitive plural, and which ones end in -ek? And are they other possible endings?
For example : matka -> matek
artysta -> artystów

[immery]

there are rules, depending on the gender and the last letters of the noun., but there are also exceptions.

but the more general tables do not show -a ending masculine nouns, so you can either find some rules here http://grzegorj.w.interiowo.pl/gram/gram00.html or just learn the declension.

[fmarkom]

How about "Oni potrzebują innych artystek?" when they would need only other female artists?

[erencetin]

Why the case is Genitive in this sentence?

[alik1989]

Potrzebować always takes the genitive case with direct objects.