Company Promotion in CRM to Customer in Sage 300 with auto assign customer number

I have a customer that we recently upgraded from CRM 7.2 and Sage 300 v2014 to CRM v2022 and Sage 300 v2022.  In their old system they had and auto-assign customer number when they promoted a company in CRM.  Clearly a custom process.  I need to set this up in the new system.  Does anyone know how to set this up?  I would be willing to pay someone to get this done.

Any and all advice greatly appreciated,