Hi Radhika,
You need to create RFC destination type H in ECC and you need to configure the RFC destination name in sxmb_adm->Integration Engine configuration.
-- Again, since there is no RFC or Idoc Adapters used in the next scenarios, I think we don't have to create any RFC Destination of Type T or 3 from ECC or XI. Do I have to create any other RFC destinations?
-> You don't need to create T & 3 type connections if your not using RFC & IDOCs
Thanks,
Satish.