postgresql 9.4 database cluster move to debian buster

I have a postgresql folder backup (no dump) from postgresql 9.4.

On my Debian Buster server I want to get this old database working, so I re-installed postgresql-9.4 with this tutorial: https://wiki.postgresql.org/wiki/Apt#Quickstart

Now it says

pg_createcluster 9.4 main --start
Configure existing cluster (configuration: /etc/postgresql/9.4/main, data: /var/lib/postgresql/9.4/main, owner: 117: 120)
Error: move_conffile: Required configuration file /var/lib/postgresql/9.4/main/postgresql.conf does not exist

I was able to start a new Cluster2: https://stackoverflow.com/a/48624460/1069083

But this one is empty. My old main cluster contains all my data.

How do I start the old main cluster?