Looking and firing towards mouse position, 2d game.

I am making a 2d game where I need my player to fire towards my mouse position when the space key is pressed.
I already have the shooting that works, but the aiming towards the mouse is where I get stuck.

Thank you very much for your help!

using UnityEngine;
using System.Collections;

public class PlayerShooting : MonoBehaviour 
{	public GameObject bulletPrefab;
	public Transform bulletSpawn;
	public float coolDown =  3f;

	void Update () 
	{
		//print ("the cooldown time is " + coolDown);
		CoolDownTimer();
		if(coolDown <= 0)
		{		
			if(Input.GetKeyDown(KeyCode.Space))
			{
				Instantiate(bulletPrefab,bulletSpawn.position,bulletSpawn.rotation);
				coolDown = 1f;
			}
		}
	}

	void CoolDownTimer()
	{
		coolDown -= Time.deltaTime;
	}
}

Try this : Camera.main.ScreenToWorldPoint(Input.mousePosition);

Any camera is fine.

use the Transform.LookAt for the bulletSpawn

and check out Input.mousePosition it’s a Vector2

destination = Camera.mainCamera.ScreenToWorldPoint (Input.mousePosition);
destination.z = 0;
direction = destination - yourPlayer.transform.position;

where destination is variable which holds the mouse position.
Hope it will work.