script.js

var client_id = pm.environment.get("client_id");
var client_secret = pm.environment.get("client_secret");
var tenant = pm.environment.get("tenant")


pm.sendRequest({
    url: 'https://login.microsoftonline.com/' + tenant + '/oauth2/token',
    method: 'POST',
    header: {
        'Content-Type': 'multipart/form-data',
          },
      body: {
          mode: 'formdata',
          formdata: [
            {key: "client_id", value: client_id},
            {key: "client_secret", value: client_sercret},
            {key: "resource", value: "https://management.azure.com/"},
            {key: "grant_type", value: "client_credentials"},
            
        ]
      }
},  function(err, response) {
  const jsonResponse = response.json();
  pm.environment.set("access_token", jsonResponse.access_token);
});