I think that means that the upgrade didn’t work. I had a similar job yesterday.
What I did, I think, was move the backup data back to postgres_data, then switch to the pg10 (probably 12 for you?) template, then rebuild, and then change the template back and rebuild twice more for the upgrade.
That’s broad strokes, but the best I can do on my phone. The PostgreSQL 13 update should have all you need.