Internal Requisition - License for OM

 Hi, 

I need to use internal requisitions for Purchasing because some departments make internal orders / requisitions to the central store, then central store sends the material and the departmentes receive the material.

We are implementing only purchasing, but we know that for internal requisitions we need to setup some features in OM. 

Is it necessary to have the license for OM to use internal requisitions?

If yes, which feature could we use to accomplish the scenario described?

Thanks!!