Breastfeeding advice

Hey all, my son was born last Friday at 31 weeks he's currently still in the nicu but they have me pumping every 3 hours or as I can. And I'm trying to get on a routine, I ideally do every 3-4 hours but I'm still in the hospital due to high blood pressure so I don't get a lot of privacy with family coming etc. Well once I get home and am able to get on a good routine with pumping, how much should I get ? Also as far as freezing some etc how does that work? I want to exclusively breastfeed him. Also right now I'm currently getting 2 ounces each time I pump ( double pump so 2 ounces out of both boobs, sometimes a little more) is that good for just starting off? I pump for about 20-30 min at a time. How much milk should I have with him being a week old ? Will I get more ?