How many maternity panty do we need?

I just given birth 2 months ago. I went through natural birth. In my experience, I bled for 3 weeks and not a lot of blood. I thought I would have heavy flow like my menses before pregnancy so I bought a lot of 40cm sanitary pads. On my 2nd week, my blood flow is lesser. By the 3rd week, I used thin kind of sanitary pads. But I would recommend to change your pad every 3-4 hours to prevent infection as the gynae will cut down there for natural birth and there will be stitches.