What is the ruling regarding my missed prayers which I abandoned out of ignorance, thinking that the blood after the miscarriage of a seven-week-old fetus was nifas blood?

If a woman aborts a fetus in which human creation is not yet discernible, the flowing blood is considered irregular blood (dam fasad) and does not prevent prayer or fasting. If human creation is discernible, then it is postpartum bleeding (dam nifas). The minimum period for human creation to be discernible is 81 days.

You erred by not praying, and you are required to make up these days according to the majority of scholars. Some scholars, however, are of the opinion that making up these prayers is not obligatory in this situation due due to lack of knowledge regarding the obligation of prayer, citing the statement of Sheikh al-Islam Ibn Taymiyyah that whoever has not been informed of a specific command from the Messenger of Allah (peace and blessings be upon him) is not bound by its ruling.

The more cautious approach is to make up these days by combining them and performing them to the best of your ability.