pg_hba.conf and postgresql.conf in old installation directory
Until postgres version 9.5 the upgrade procedure was to

create a new fresh database cluster using the new version
make a full dump of the old cluster
read the dump into the new cluster.

the selection of the cluster depends on the PGDATA environment variable.
the version of the cluster software version depends on the PATH environment variable.
Make sure they match your needs. The setting is done in the startup scripts and can be copied for the client.