If you used desktop software downloaded/installed from a CD to your own computer, then the tax files are stored locally on your own hard drive or any backup device you used like a flash drive. They are not stored online. If you cannot recover them due to a hard drive failure, etc. you can get a free transcript from the IRS or for a fee of $30 an actual copy of your tax return.
I assume you don't have any backups or a printout of your tax returns? You will have to do 2025 next year from scratch. Other than transferring to next year is there a reason you need them? Like do you have any carryovers or items like depreciation?
You would have to install the programs again by downloading them from your online account. Then manually enter everything into a new return. If you do the oldest year first and it matches your filed return or comes out close you can transfer it into the next year to start the next year return and so on. If you get 2024 filled out you can transfer it into next year.
Did you use Turbo Tax before the last 2 years? Do you have any older .taxyyyy or pdf files?
Do you have the tax file ending in .tax2021? Did you use the Desktop programs or the Online versions? The only thing you could do (but it would be a lot of work) is to transfer the 2021 tax file into the 2022 desktop program and fill out 2022. Then transfer the 2022 tax file into the 2023 program and so on to get current. If you used the Desktop programs you should be able to install them again, either from the CD or the download.
2021 will not be of any help in doing Turbotax 2025. you'll need to start from scratch. you should get at a transcript (or copy) for the missing years. 2024 may have info that needs to be entered on your 2025 return, the IRS only retains returns for 7 years after that they're permanently deleted. Turbotax only supports the app for 3 years prior to the current year. Currently 2021, with maybe an exception for a few earlier years, is the earliest year that can be opened with the app. after that they cannot be opened even if you have that year's app.
it's advisable to store a pdf copy of each year offline