Your authority to handle dad's affairs with the POA expired when he passed, the executor of his will now has authority. If he has no will and whatever assets he had don't list a beneficiary, you are going to need the advice and services of an attorney.
Depending on the laws in your state and how much dad's assets are worth, the resolution will be either more or less complicated.
Depending on the laws in your state and how much dad's assets are worth, the resolution will be either more or less complicated.