@tassoman I would follow the install guide for the new server, up to the point of creating the database. Then copy over prod.secret.exs, nginx conf, and probably SSL certs.
For dumping, pg_dump -Fc pleroma > pleroma.dump works great. Then for importing, you want pg_restore -j 4 pleroma.dump. Replace 4 with the number of CPUs you have, it will go way faster.