You take J train until last stop or i believe F train it'll stop at last stop near hillside avenue then u can walk from there to Nassau buses (if that's where you're needing to go)
You will need to check the various bus companies, such as Peter Pan and Greyhound, that leave from or go to port authority. You can't really get that answer here. There are also buses that go to various locations in NJ that leave either from within port authority or across the street from it. An internet search will be your best bet.
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