Make a `where` in FireBase with Ionic

I have my BD in firebase but I want to do a where, as a login ie if I enter the user and the password brings me the corresponding data.

This is my BD in firebase:

wSNuE

An example:

When I send the emailand telefonoto tb01_usuariobring me the corresponding data:

Currently I am doing it only with the ID that is similar to the field telephone, but I need to do it with the two fields that are inside each record, I hope they understand me

verifica_usuario(telefono: string) {

    email = email;
    telefono = telefono;

    let promesa = new Promise((resolve, reject) => {
      //this.items = afDB.list('/cuisines');
      this.af.list('/tb01_usuario/' + telefono)
        .subscribe(data => {
          if (data.length === 0) {
            //clave no es correcta
            resolve(false);
          } else {
            //clave correcta
            this.telefono = telefono;
            this.guardar_storage();
            resolve(true);
          }
        });
    })
      .catch(error => console.log("ERROR en promesa Service: " + JSON.stringify(error)));

    return promesa;
  }