Fade between scenes

Hi all, I have a JS script in which if a variable reaches 3, the next scene loads. How can I make the scene fade in instead of abruptly switching?

Here's my code:

 #pragma strict
 import UnityEngine.UI;
 import UnityEngine.SceneManagement;
 
  var theImage:UnityEngine.UI.Image; 
  var theSprite:Sprite; //The image you want to drag in the inspector
  static var clickCount = 0;
 
 function OnMouseDown () {
   theImage.sprite = theSprite;
   clickCount++;
   Debug.Log(clickCount);
   if (clickCount == 3){
   loadLevel();
   }
 
 }
 
 function Update () {
 
 }
 
 function loadLevel (){
 
      SceneManager.LoadScene("Final"); 
 }

Thanks!!