Everyone is different, but count on at least a few weeks. The first week, maybe two will be heavy, small clots but the big clots should only be in the first like two days. The rest of it should be less, like a light period and then spotting. Sometimes it stops for a day or a few days, and then re-starts. It should be less than a vaginal birth because they suction some of it during the section.
You won't need adult diapers, if it's that heavy then something is wrong and you need to go to the hospital. You'll need pads (tampons are not okay to use right after delivery, no matter what type), the big size with wings, and for the really heavy days right after, my hospital always provided really humongous ones. They also provided mesh underpants to wear instead of using (and therefore ruining) my own.
