Is the questioner sinful for keeping some items bought with stolen cards, and what is the ruling on his prayer in clothes bought in this way or on flooring installed likewise, and must a computer bought in the same way be disposed of?

Sincere repentance is obligatory, and the stolen money must be returned to its owners. If it is impossible to reach them, then it must be given as charity to the poor and needy to clear one's conscience. The conscience is only burdened by the stolen money.