How to Set Up Finder in Big Sur

I just updated from Yosemite to Big Sur. In Finder, the left hand column with folders is missing: Dropbox, Amazon Drive, Documents, Photos, Applications, Downloads, etc. How do I restore the left hand column with the folders? I saw another post with this question––The answer suggested dragging the "favorites folder." I don't see a favorites folder... I'm not seeing any folders at all, just individual files. I can't tell where (Dropbox, iCloud, OneDrive, etc) the files are stored.