What should I do with money I wrongfully took from a foreign company that has closed, given that I don't know the amount or to whom I should pay it?

I congratulate the questioner on their repentance and pray for their steadfastness. They should then estimate the amount they took or caused the company to lose, and give it to the company owners or their heirs. If they cannot be found, they should donate it on their behalf, with the option, if they are later found, for them to either approve the charity and its reward for themselves, or take the money and its reward for the questioner. If they were non-Muslims, the money must be delivered to them or their heirs if possible. Otherwise, the amount becomes fay' (war booty or state revenue) and should be spent on the welfare of Muslims, not given as charity on their behalf.