SCRIPT - C# Script Error CS1061 !

This is the error message :

Assets/SCRIPT/EnemySpawn.cs(13,32): error CS1061: Type `UnityEngine.GameObject' does not contain a definition for `Length' and no extension method `Length' of type `UnityEngine.GameObject' could be found (are you missing a using directive or an assembly reference?)

This is my script : ( the error is on line 13 )

using UnityEngine;
using System.Collections;

public class EnemySpawn : MonoBehaviour {

	public GameObject Enemy;
	public int amount;
	private Vector3 spawnPoint;

	void Update () {
	
		Enemy = GameObject.FindGameObjectWithTag ("Zombies");
		amount = Enemy.Length;


	}
}

Your problem is this Enemy.Length. You have Enemy defined as a GameObject

public GameObject Enemy;

and GameObject does not have a member Length. From looking at your code, it looks like you want to do something like this

public GameObject[] enemies;
enemies = GameObject.FindGameObjectsWithTag ("Zombies");
amount = enemies.Length;

So your code would actually be this

using UnityEngine;
using System.Collections;

public class EnemySpawn : MonoBehaviour
{
    public GameObject[] enemies;
    public int amount;
    private Vector3 spawnPoint;

    void Update ()
    {
        enemies = GameObject.FindGameObjectsWithTag ("Zombies");
        amount = enemies.Length;
    }
}