Hi Palichuk
You should think of milk pumps as electric massagers. Do they work to enlarge the breasts? Probably yes, in the same way as massage does. Also, people repport nipple and areola enlargement using them (which makes sense). Make sure you have a set of flanges adaptors to find the right size for your nipples. (Amazon has them)

Personally, I love milk pumps and my boobs always feel heavier  after a session.