What train should i take to prospect park nyc from 42nd st?

I from jersey the bus leaves me in 42nd infront of port authority from there I want to taqke the train to 9th street & prospect park west I was thinking of taking the q train ut I'm not sure since I don't really take trains that often can any new yorker show me the way there by telling me what train I should take….? Back and return? If itsn a prolem thanks