What should I do with the money I acquired from stealing a computer and selling it with my friends during adolescence, and how can I repent to Allah if it is difficult to return the money to its owner or to contact my friends who shared in the theft?

You must return the value of the device you stole on the day of the theft. You are not required to inform the owner of the theft; rather, it is sufficient to return the right to him by any possible means. You must return the full value, as you are a guarantor for the device due to your participation in the theft, with the possibility of claiming from your partners what you paid on their behalf. It is not permissible to give the value of the device in charity as long as you are able to return the right to its owner.