Finding Vector3 position of GameObject

Hello, I need help with spawning a cube at the “gun” object, I got it working with fixed coordinates but do nowt know how to do it with something that moves, this is the error I get now:

Cannot implicitly convert type UnityEngine.GameObject' to UnityEngine.Vector3’

using System;
using UnityEngine;
using UnityStandardAssets.CrossPlatformInput;

public class Shoot : MonoBehaviour {

	public int m_Ammo;
	private Vector3 gun = GameObject.Find("Gun");

	// Use this for initialization
	void Start () {

	// Update is called once per frame
	void Update () {
		if (CrossPlatformInputManager.GetButtonDown("Fire1") && m_Ammo >= 1)
			GameObject cube = GameObject.CreatePrimitive(PrimitiveType.Cube);
			cube.transform.position = new Vector3(gun);

gameObject.transform.position is the Vector3 “gun” object location you are looking for