Praise be to Allah.
If he was conscious during that time then he has to make up the missed prayers, standing, sitting, lying on his side, according to what he is able to do. He should do them in the right order, with the appropriate intention. So he should pray the prayers of the first day in order, starting with the first obligatory prayer that he missed, then the next one and so on, then the prayers of the second day and the third day, until he finishes. But if he was unconscious, in that case he does not have to make them up.
And Allah is the Source of strength. May Allah send blessings and peace upon our Prophet Muhammad and his family and companions.