How can I atone for defrauding in merchandise from which I did not financially benefit, and three years have passed, making it difficult to determine its amount or its owners who are dispersed in different cities, knowing that I have repented for that?

You must strive to reach those whom you defrauded to return their rights to them, estimating the amounts by your best judgment if you do not know them. As for the money that you are unable to return to these defrauded individuals, or if you cannot reach them, then it must be spent for the benefit of Muslims and in charitable causes, as a charity on behalf of its owners.