What I did in the first place was to remove C8.0.3 from control panel.
Then installed 8.5 and it imported all my preferences correctly without the need to do anything else.
I have to ask, where were your projects installed that they would disappear with an uninstall?
As a suggestion … I keep all projects in a Projects folder on a second drive (with sub-folders for each project). You may want to consider this for your own setup.