It is very easy to locate all your SketchUp files on your computer. In case you're having trouble locating your SKP files after upgrading., follow this quick tip:
For Windows:
Open File Explorer on the taskbar or use Windows Key+E
In the search box at the top right corner, type in *.skp and this will locate all SKP (SketchUp files) on your computer regardless of the filename.
For Mac:
Open Finder, click your username next to the house
Search "kind:skp" and it will show you all SKP files on your Mac