curl --request GET \
  --url https://api.hubapi.com/marketing/v3/marketing-events/{externalEventId}/identifiers \
  --header 'Authorization: Bearer <token>'

{
  "results": [
    {
      "externalEventId": "<string>",
      "marketingEventName": "<string>",
      "objectId": "<string>",
      "appInfo": {
        "id": "<string>",
        "name": "<string>"
      },
      "externalAccountId": "<string>"
    }
  ],
  "total": 123
}