What is the expiation required from someone who has not fasted or prayed for 28 years? And how can he make up for the missed prayers and fasts?

Prayer and fasting are two pillars of Islam. Therefore, whoever denies the obligation of either of them has committed an act of disbelief that expels him from the fold of Islam. As for abandoning them while acknowledging their obligation, it is a grave sin. And abandoning prayer is an act of disbelief, according to the preponderant opinion, based on the Prophet's (peace be upon him) saying: "The covenant between us and them is prayer; whoever abandons it has disbelieved." And whoever repents with sincere repentance, Allah will accept his repentance. He is not required to make up for the prayers and fasts he missed in past years, because sincere repentance for abandoning prayer demolishes what came before it, and religious obligations become binding upon a Muslim at puberty.