You couldn’t use a power of attorney anyway because a power of attorney dissolves at death. In order to file any financial reports or tax returns for your father after his death, you need to be appointed the administrator of his estate, or at least the US portion of his estate. This will require a visit to the probate court in your state. If his estate is small and uncomplicated, you may be able to file a simple form with the clerk of the probate court. For large or complicated or contested Estates, the process may be more complex.
