I am trying to configure Microsoft Dynamics 365 connector using Web API.
I do have all the credentials other than client identifier
Where I can get client identifier ?
This info should be provided by Dynamics. I think you should have a clientId assigned to your app.
See here for how to get it: How to get Client ID and Client Secret Key in CRM 2016? - Microsoft Dynamics CRM Community Forum or Walkthrough: Register a Dynamics 365 app with Azure Active Directory