Is a prize from a usurious bank permissible after its conversion to an Islamic bank, and is Zakat obligatory on it?

The prize resulting from an interest-based account is ill-gotten gain (haram earnings), and the bank's later conversion to an Islamic bank does not make it permissible. It is not permissible to take these prizes because they are usury (riba), and one must dispose of them by giving them to the poor and needy. It is permissible for the one who possesses it to benefit from it if he is poor and in need, just as it is permissible for him to give charity from it to himself and his dependents if they are poor. The prize should not be left to the bank so that it does not combine benefiting from the deposit amount and usury, and there is no zakat due on it because it is ill-gotten wealth.