I have a company that runs Filemaker Pro databases for managing some parts. And they have considered using SAP recently. How much product/inventory/sales/etc..

I have a company that runs Filemaker Pro databases for managing some parts. And they have considered using SAP recently. How much product/inventory/sales/etc... processes is required before you should move from FMP to something like SAP? Is it number of users, client accounts, employees, products? What is the break point for needing ERP (Enterprise Resource Planning) software?