Must the missed prayers be made up by Muslims in Kazakhstan who were unaware of their obligation due to the atheistic regime, knowing that making them up would be difficult for them?

If the Kazakhs are ignorant of Islamic rulings such as prayer and fasting, and know nothing of Islam except that Allah is their Lord and Muhammad is His Messenger, then they are excused for their ignorance, and they are not required to make up the prayers and fasts they missed.