Determining Cost Basis on TOD property

My brother and I received property via a Transfer on Death deed, legal in our state. We did not have the property appraised when my mother died, in November 2022.  The county assessment for 2022 is about $50,000 less than the 2023 appraisal.  Is there a good way to determine what our cost basis would be as we sold the property in May 2023?