Mail folders are empty in Mail on Mac, but appear on iPhone

My mail folders don't have anything in them on my Mac, but they do on my iphone. I'm running Tahoe 26.6.2 on a relatively (year old) Mac. On my old Mac, I could set up folders in Mail, either "on my mac" or "Google". But I'm at wit's end trying to figure out why my mail folders are now empty even though I've been dragging emails into them for years.