Which directories to provide for pg_upgrade?

Question

I have docker container with postgres 12 and I want to upgrade it to 13. This image stores data and configs in /var/lib/postgresql/data dir:

1. show data_directory; returns that directory
2. postgresql.conf is stored in that directory

I tried to execute pg_upgrade with that directory (in old pg12 volume) as old data and config directory argument: docker run --name migrate13 -v pg12_volume postgres:13 su postgres -c "cd /tmp && pg_upgrade -b /var/lib/postgresql/data -d /var/lib/postgresql/data -B /var/lib/postgresql/data13 -D /var/lib/postgresql/data13"

Error check for "/var/lib/postgresql/data/postgres" failed: No such file or directory is returned. I failed to find what this error means: I provided wrong data or config directory?

What right directories should contain and how to find them?