How can I reuse an variable that has been instanciated

Hello i’m a begginer in Unity and I have a little problem.
I want to reuse for exemple, the variable “issou” in the start() , but I can’t because it’s a local variable.
But how can i do for exemple if I want to change the variable position or something ?

Thank You.

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class GenerationTerrain : MonoBehaviour {

    public GameObject cube;

	// Use this for initialization
	void Start () {

        // instanciation de trois morceaux de terrain

        var issou = Instantiate(cube, transform.position = new Vector3(1,2,3), transform.rotation);
        issou.transform.localScale = new Vector3(10000, 100, 1000);
        issou.GetComponent<Renderer>().material.color = Color.red;

        var issou2 = Instantiate(cube, transform.position = new Vector3(1000, 2, 3000), transform.rotation);
        issou2.transform.localScale = new Vector3(10000, 100, 1000);
        issou2.GetComponent<Renderer>().material.color = Color.green;

        var issou3 = Instantiate(cube, transform.position = new Vector3(2000, 2, 6000), transform.rotation);
        issou3.transform.localScale = new Vector3(10000, 100, 1000);
        issou3.GetComponent<Renderer>().material.color = Color.blue;


    }


	// Update is called once per frame
	void Update () {

	}
}

Simply change the scope of your issou variable. I.e., you can place it below “public GameObject cube;” as “public GameObject issou;”.