Do a where in FireBase with Ionic 3

I have my DB in firebase but I want to do a where (I know there is no WHERE in a DB NoSQL but there will be some search function), like a login that is if I enter the user and the password brings me the corresponding data of a registration.

  

This is my BD in firebase:

An Example:

  

When I send the email and telefono to tb01_usuario bring me the   corresponding data if the parameters match:

     

Currently I'm doing it only with the ID that is similar to the telephone field, but I need to do it with the two fields that are inside each record, I hope you 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;
  }