I was my Father P.O.A. until he passed a few month ago. what's my next step to do to protect my Father asset that I found out about.

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.