Lost my .tax2020 file and need to amend my 2020 taxes

I have lost my .tax2020 file! I have all the PDF and forms but the .tax is missing. I have backup on three devices and all three are gone? I searched *.tax2020 and found only one return for my daughter. The three others from three other family member returns are missing? How can I proceed with the amended return? Do I have to start all over and create a new file to then amend? Help.....