In 19.3 and 2020, autosave (aka, recovered) files are stored in the following locations.
Mac
~/Library/Application Support/SketchUp 20xx/working/SKETCHUP/RecoveredFiles
Win
C:\Users\YourUserName\AppData\Local\SketchUp\SketchUp 20xx\SketchUp\working\SKETCHUP\RecoveredFiles