Hi abhinav,
That doesn't seem to be the correct URI . Could you please answer below quetsions
1) Firstly is this a standard or custom app
2) Does it use Odata service to connect to SAP ECC backend ; If so URL should be something as below
http://<<SAPserver domain>>:<<PORT >>/sap/opu/odata/sap/<SERVIC NAME>/$metadata
If so , yes it would ask you for user name and password to connect to SAP server , which shoud be SAP user credentials.
Hope this helps.
BR,
Rini