Hi everyone! I start back at work full-time in...

Hi everyone! I start back at work full-time in early May by which stay my little one will be 4 months. I would like to express until she is about 6 months so plan to start now and store them in the freezer. I had a few questions: 1) How many mls would I need to give her per feed when she is 4 months? 2) Where is a good place to buy freezable breast milk storage bags? (does anyone recommend a good brand) Are they re-useable also? 3) When I stop breatfeeding at 6months and switch to formula and solids what is the best way to stop it hurting? 4) What is the best forumla to switch to at 6 months? Thanks for any help! Love Bel and Mia