Postgresql.conf not found
If you wish to know under which settings PostgreSQL is currently running, one good way to do it is to have a look at the pg_settings view:

SELECT name, setting, context
FROM pg_settings
WHERE name LIKE '%conf%';


I've added the context column to know how new values will be taken into account (a server restart, a config reload, ...).

You could also use the SHOW command:

SHOW config_file;