1) Identify the path where your local backup structure is stored:
# grep DUMP_D /etc/psa/psa.conf
2) Descend to that path, for example
# cd /home/my_local_backup_storage
3) The data that is related to one specific user from your server is stored in the /clients/<user name> subdirectory. So its full path for the example would be
/home/my_local_backup_storage/clients/<user name>