Did you use the Desktop program? Do you still have it installed?
The tax files (and PDF files) should be in your Documents then in a Turbo Tax subfolder.If you can't find them do a search for all files ending in .tax or .tax2018, .tax2017 etc.And check the Recycle Bin.For Windows 10 check the One Drive. Did you make any backups? Like DropBox.
If you don't have the main .tax file you might have one that starts with a Tilde sign ~ like
"~your name.tax2018".That file is if your computer crashes or your real file gets lost or deleted or corrupt so you can restore it.
Did you save your return? In Windows you have to manually save, although it will ask if you want to save when you exit the program or switch to another return.
Try this......start the 2017 program. Then go up to File-Open and see if it finds your file.