Advise please-going back to work

Erin • Mom of two boys 7 & 5 and just welcomed Estella June 6-29-15' 💙💙💗
Tomorrow is my official day to start back to work blah! Anyway I'm currently exclusively nursing my daughter with a couple pumps a day for storage. My question is how many times should I pump at work? I currently pump after first morning feed & plan to continue that which will typically be around 6:30-7am getting 5-8oz & also pump while she's napping in the afternoon getting only 3-5oz. So including the 7am pump should I pump 3x at work or would 2 be enough? Since she nurses all day I don't know what I might pump out on those sessions? And to be honest I'm not 100% sure how much she'll need at each feeding she has rarely had to take a bottle (which might be bad for our sitter 😕). I do have a freezer full so I do have a back up, I'd just love some of your insight! Thanks!