Customize User Pro plugin - automatically assign a member number to user profile

Hello, I have a test site located here: [login to view URL] Requirements: A new website user will have the capability to register as a New Breeder on this form here: [login to view URL] The user will then be given a registration number automatically from the site that looks like this: GCA-445566 (GCA always stays, but 445566 are the dynamic numbers). This I would like to be stored in the user profile on the front end of the site and also on the admin area of the site under the user profile information. Once the number is created, it can never be revised. Once the "New Breeder" registration has been completed and approved for use (functionality already exists). The user can then fill out other forms on the website. The forms should pre-populate with the breeder number (GCA-445566) if they are logged in. Currently, I have a plugin called UserPro installed to take care of the user profiles. This is where you would need to edit files to get the registration number working upon New Breeder Registration. I also use Ninja Forms for the other forms on the website such as [login to view URL] where the Breeder will register puppies. There may be a need to install an add on or custom code to ninja forms to get the breeder user registration number to auto-populate. I see an add-on here that may help: [login to view URL] . I can purchase this and install if needed.