How can a person share the profit from investing orphans' money and the financial prize he won from an Islamic bank with the orphans' money itself?

It is obligatory to pay off debts to their owners when able, or to obtain their release from it. Investing and growing an orphan's money is a good deed, and this includes trading with it for a known percentage of the profit, provided that the transaction is safe in its outcomes and permissible. It is permissible for a poor guardian to consume from the orphan's money in a reasonable manner. As for the prize from the account, if it is exclusively for the orphans' money, then it belongs to them. But if your personal money is mixed with the orphans' money, then the prize is to be shared between you.