AngularJS variable scope problem

I have created a var to count numbers of drivers from firebase. I want to display it into the HTML, but I can’t solve the $scope problem. Can anyone help me?

In my Js file

 db.collection("drivers").get().then(function (snap) {
        $scope.size = snap.size;
        console.log('numbers of drivers:',$scope.size); // gives the correct number in the console

// In my HTML part 

{{ size }}