Copy

            POST /B2C_1A_DP_ClientCredentialsFlow/oauth2/v2.0/token HTTP/1.1
            Host: myd3identity.onmicrosoft.com
            Content-Type: application/x-www-form-urlencoded
            Content-Length: 234

            grant_type=client_credentials&scope=https%3A%2F%2Fmyd3identity.onmicrosoft.com%2Fhttps%3A%2F%2Fmyd3identity.onmicrosoft.com%2F8ff73c8a-2841-41eb-9a63-c554f17404b4%2F.default&client_id=YOUR_CLIENT_ID&client_secret=YOUR_CLIENT_SECRET