What should my friend do to repent for stealing from the hotel and its guests, given that he does not know the amount of money stolen?

The brother is obliged to repent and feel remorse, and to resolve not to return to the sin. He must return the money he took to its owners (the hotel owners or their heirs). If he cannot reach them, he should give it as charity on their behalf. If he finds them afterward, he should give them the choice between letting the charity remain theirs or taking their money. If he does not remember the amount, he should act based on his best judgment, prioritizing the rights of others to clear his conscience. The money must be returned to the hotel owners because it is their right, even if it is more than they specified.