1146 Table DB.configuration does not exist

I'm fairly notice at PHP , mysql

testing locally on new install of version 1.3.9h

using DB from online store version 1.3.9g but had upgrade to 1.3.9h

had initial issue with DB and fixed by adding prefix in admin/includes/configure.php

define('DB_PREFIX',' znc_'); which must have been the online install default

can now access admin page , but when I use online catalogue to view the site I get the following error:

1146 Table 'db_name.configuration' doesn't exist
in:
[select configuration_key as cfgkey, configuration_value as cfgvalue from configuration]

I assume I need to change an additional file somewhere to have the DB prefix defined as I did in
admin/includes/configure ('DB_PREFIX',' znc_');

is there a separate configure file as I can't see anywhere in the admin/includes/configuration .php code where it's clear I might need to change the prefix

You have 2 configuration files:
/includes/configure.php
/admin/includes/configure.php

And, to make changes to them, you need to make them writable, since they're normally set to read-only. You can't upload or save changes to a read-only file.

Thank you so much! so simple and yet it had me dumfounded !