My inventory scripts

I started following this tutorial on youtube and I got to a point where their is just one error from stopping me. Then I researched it a lot of people had this problem but so I found a completed version of the script that was released online I tested it out and I still get the single error.

//my error Assets/my menu/FOLLOW ME/MYGUI/MyGui.cs(13,22): error CS0246: The type or namespace name `Item' could not be found. Are you missing a using directive or an assembly reference?

 using UnityEngine;
 using System.Collections;
 using System.Collections.Generic;
  
 public class myGUI : MonoBehaviour {
         public float lootWindowHeight = 90;
        
         public float buttonWidth = 40;
         public float buttonHeight = 40;
         public float closeButtonWidth = 20;
         public float closeButtonHight = 20;
        
         private List<Item> _lootItems;
         private bool _displayLootWidnows = false;
         private float _offset = 10;
         private const int LOOT_WINDOWS_ID = 0;
         private Rect _lootWindowsRect = new Rect(0,0,0,0);
         private Vector2 _lootWindowSlider = Vector2.zero;
         private GameObject chest;
  
         // Use this for initialization
         void Start () {
                 _lootItems = new List<Item>();
         }
        
        
         public void OnEnable() {
                 Messenger<int, GameObject>.AddListener("PopulateChest", PopulateChest);
         }
        
         public void OnDisable() {
                 Messenger<int, GameObject>.RemoveListener("PopulateChest", PopulateChest);
         }
        
         // Update is called once per frame
         void Update () {
         }
         void OnGUI() {
                 if(_displayLootWidnows)
                 _lootWindowsRect = GUI.Window(LOOT_WINDOWS_ID, new Rect(_offset, Screen.height - (_offset + lootWindowHeight), Screen.width - (_offset * 2), lootWindowHeight), LootWindow, "Loot Window");    
                                        
         }
                        
         private void LootWindow(int id) {
                 if(GUI.Button(new Rect(_lootWindowsRect.width - 20, 0, closeButtonWidth, closeButtonHight), "x")) {
                         ClearWindow();
                 }
                
                 _lootWindowSlider = GUI.BeginScrollView(new Rect(_offset * .5f, 15, _lootWindowsRect.width - 10, 70), _lootWindowSlider, new Rect(0, 0, (_lootItems.Count * buttonWidth) + _offset, buttonHeight * _offset));
                
                 for(int cnt = 0; cnt < _lootItems.Count; cnt++) {
                         GUI.Button(new Rect(5 + (buttonWidth * cnt), 8, buttonWidth, buttonHeight), cnt.ToString());
                 }
                
                 GUI.EndScrollView();
         }
        
         private void PopulateChest(int x, GameObject go) {
                 chest = go;
                
                 for(int cnt = 0; cnt < x; cnt++) {
                         _lootItems.Add(new Item());
                        
                         _displayLootWidnows = true;
                 }
         }
        
         private void ClearWindow() {
                 _lootItems.Clear();
                
                 chest.GetComponent<Chest>().OnMouseUp();
                
                 chest = null;
                 _displayLootWidnows = false;           
         }
 }