If you don't have a backup of the file ending in .tax2019 you would have to first recreate your original return. Do you have a print out you can use?
You can recreate the original return using the Forms Mode. Then when it matches each line you say to mail it and print it out so it thinks it was filed. Then you can amend. How to amend a Desktop return,
https://ttlc.intuit.com/community/amending/help/how-do-i-amend-my-return-in-the-turbotax-cd-download...
