Hi Aditya,
SAP Process Integration and Process Orchestration are basically the same for what B2B integration is concerned.
Please read several articles concerning the B2B add-on within this community and will have a clear view what is all about.
Off course you will need mappings etc, but with the B2B add-on from SAP, this is easier than e.g Seeburger software.
Kind regards
Dimitri
