Hi Namita,
Did you opend the Service in tcode SEGW already? There you can see if there is maybe a mapping for the Entitysets. If so you can see the Name of Functionmodul, DDIC etc. If there is no mapping you have to go into ABAP Coding.
In SEGW under Runime Artifacts you will find different Classes. There please rightclick on *DPC* class and open it in ABAP Workbench. Inside Workbench search for a method called like this
<ENTITY>_GET_ENTITYSET
Regards
Max