Need basis help

Hi there. I am a CPA in Indiana and had a client sell her mineral rights that she inherited about 10 years ago. Prior to the sale, there has never been any drilling on her land. She actually didn’t know about the land/rights until she was contacted by someone last year and sold the rights at that time. Trying to come up with a basic determination of her stepped up basis in the property. I have seen a few similar questions but am not sure how to message anyone directly to get contact information.

Any help is greatly appreciated.