Hello Vishwanath,
Vendors are replicated from ECC to SRM, which means, the business partner for vendors exist in table BUT000. Right?
If yes, then you need to provide bidder role BBP001 in transaction BP and create a business partner as contact person in relationships section of transaction BP .
If you have to automate this for large number of vendors, then update the following tables - BBPM_BUT_FRG0010 - FM BBP_BUPA_FRG0010_CREATE / BBP_BUPA_FRG0010_CHANGE
BBPM_BUT_FRG0020 - FM BBP_UPDATE_FRG0020
For contact person -
Use FM BBP_CREATE_CONTACT_PERSON to create a contact person.
You can create a program to get the details of BUT000 table and create bidder role and contact person. Schedule a job for this for new vendors.
Hope this helps!!