What should I do concerning the twenty days in which I did not pray, given that my bleeding did not stop until sixty days after childbirth, and I was ignorant that a woman becomes pure after forty days and is obligated to pray, and I only learned of this ruling nine months later? And when should I make them up, if that is incumbent upon me?

Scholars differed regarding the maximum duration of nifas (postnatal bleeding). The majority of scholars held that it is forty days, based on the hadith of Umm Salama (may Allah be pleased with her), and this is the more cautious opinion. Some scholars, like Imam Al-Shafi'i, said it is sixty days. Sheikh Al-Islam Ibn Taymiyyah said there is no maximum limit for it; rather, the default for blood discharged due to childbirth is that it is nifas as long as it does not cease.

You are obligated to make up the prayers you missed after the forty days. If it is difficult for you due to their large number, then make them up according to your ability, even if it takes several days.