I want to reload my arrows automatically

Title shows all.
I’m making shooting game.
Here is my C# script.

using UnityEngine;
using System.Collections;

public class arrow : MonoBehaviour {

// Use this for initialization
void Start () {
}	
// Update is called once per frame
void Update () {
	if (Input.GetKey(KeyCode.Space)) {
		rigidbody2D.velocity = new Vector2(8,rigidbody2D.velocity.y);

}}}

I want to be able to load 10 arrows so that I can keep shooting 10 times.
I know it might be easy, but I’m not familiar with unity.
Somebody help me!

start with creating an int that will be how many arrows you have fired and have a bool that makes sure you can or cant shoot when you fire add one to the int and keep going until its 10 then chnage the bool to false so that you cant shoot then when you press a key it resets the ammo to 0 then to make it automatic just make it so that when ammo = 10, ammo = 0