How to keep count of enemies left

How I can check how many gameobjects with tag: “enemy” there is left in the scene, and after that it gets to zero then it will change level to another scene. I’m learning c# so I would prefer help on that language.

using UnityEngine;
using System.Collections;

public class gameobjects : MonoBehaviour {

	// Use this for initialization
	int enemiesLeft = 0;
	bool killedAllEnemies = false;
	void Start () {
		enemiesLeft = 10; // or whatever;

	}
	
	// Update is called once per frame
	void Update () {
	GameObject[] enemies = GameObject.FindGameObjectsWithTag("enemy");
		enemiesLeft = enemies.Length;
		if(Input.GetKeyDown(KeyCode.A))
		{
			enemiesLeft --;
		}
		if(enemiesLeft == 0)
		{
			endGame();
		}
	}
	
	void endGame()
	{
		killedAllEnemies = true;
	}
	
	void OnGUI()
	{
		if(killedAllEnemies)
		{
		GUI.Label(new Rect (0,0,200,20),"all gone");
		}
		else
		{
			GUI.Label(new Rect (0,0,200,20),"Enemies Remaining : " + enemiesLeft);
		}
	}
	
}

something like this maybe.

Array1=GameObject.findGameObjectsWithTag(“Enemy”);
void Start(){
Array1=GameObject.findGameObjectsWithTag(“Enemy”);
}
Void Update(){
Array1=GameObject.findGameObjectsWithTag(“Enemy”);
textBox.text=“”+array1.length+ “/” + array1.length;
}
@Reefer ,take another array of game object like totalEnemies and save the enemy tag in it, and then assign it to your text field like this TargetTextBox.text=“”+totalEnemies.length;
and also assign same enemy tag to enemy game object array in start function.
this will give you something like this Enemies: total/remaining.