The amounts on the forms your received (1099-C) are essentially income to your mother's estate and should typically be reported on Form 1041.
See https://www.irs.gov/instructions/i1041#en_US_2021_publink1000285932
The relevant issues at this point are whether or not your mother's estate had assets, whether the estate was closed properly (e.g., creditors notified), and whether the assets (if any) were distributed and to whom.
You might want to consult with local legal counsel and/or a tax professional for this matter.
