We are about to switch to Firebase notifiaction API from Parse.com (that are retiring their service in jan 2017) to send push notification to our android and iOS Apps.
I think you're looking for the FCM Diagnostics and Statistics feature.
However, this is not visible in the Firebase Console, only in your Google Play Developer Console. And the feature only works if your app is at least in Alpha Testing.
When you send notifications from the Firebase Notifications console, you get statistics about how many people received and opened the messages. But there is no API (yet) for Firebase Notifications.
If you're using the Firebase Cloud Messaging API (https://fcm.googleapis.com/fcm/send), the message statistics don't show up in the Firebase Notifications console. You can (as AL. says) get delivery statistics in the Google Play Developer Console in that case.
firebase allows you to view sent/delivered/opened statuses by default from their website http://console.firebase.google.com at the notification section
but I am not sure about the parse.com implementations
also if you are a new comer to firebase let it collect user data for about 24 hours after successfully migrating to firebase I found that in the first day the notifications weren't really reporting immediately