Supplier Site Data resides in which REST API

Hi,

Business is trying to build a dashboard / KPI metric in APEX, to find out the variation in payment term in Supplier Master (At Supplier Site Level) vis-a-vis the payment term at Invoice Header Level against the Supplier Site

Would like to seek inputs in identifying the name of REST API which holds the Supplier Site level data and how this shall be integrated with APEX

Thanks,

Saurabh Singhal.