Breast milk supply

Lizette • I have 2 beautiful baby girls🎀and now expecting baby number 3, another baby girl🎀💞💗 You can never have enough PINK!!
So how does it work when you want to pump milk while baby sleeps to build milk supply??? I want to pump & freeze milk so I have enough milk stored so when I return back to work by August.... My daughter is 6 weeks. So she eats every 2-3 hours right now.