How can one make up for years of missed prayers, given that their number is unknown, and is it obligatory to make up a missed prayer with every daily performed prayer?

According to the majority of scholars, missed prayers must be made up intentionally. This making up should be done within one's capacity, without harming the body or livelihood. The Malikis hold that making up two days' worth of prayers with each day is sufficient, and by doing so, one's obligation is fulfilled.