How much to pump?

Ashley • NurseRN💉 wife💑puppy mom🐶 mom to wonderful little boy born 5/22/18❤️👶

I’m going back to work the beginning of August. I work three days a week for 12 hour shifts. Anybody else in this situation or have any advice on how much to pump before I go back to work? How much should I stash up as he will be a little over 2 months old? I’ve pumped a couple of times and can get 2 ounces during the day and in the morning can get 4 oz.