Post code validation

Hello everyone,

I want to restrict user to enter only 6 digit post code(pincode). On quick checkout registration form I have done it successfully by changing condition in page "catalog>controller>journal3>checkout.php" but in "Add Address" page I am not able to do the same. I checked each and every controller but cannot find any validation for this particular page.
I am using Journal-3.1.3 theme with OC-3.0.3.6

Thanks

Already asked Journal Themes about that? OC is not related to Journal,
nor does it create any money from Journal Sales ...
https://support.journal-theme.com
or then check here:
https://www.facebook.com/groups/192229314684939/