How to, with a button, switch to another level when all items are collected?

Hi everyone ! Hope you’re doing great. Here’s my problem : kinda like everyone I teach myself Unity basic stuff by modifying the Roll-A-Ball tutorial. What I want to do is to change the scene by letting the player click on a button that needs to appear after he collected all of the items.
So I made de UI button that works with this script :

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.SceneManagement;

public class SceneSwitch : MonoBehaviour {

    public void ScenceSwitcher()
    {
        SceneManager.LoadScene(2);
    }
}

The button works just fine however it shows up before collecting the items. So how am I supposed to code a “when score reaches X items the button shows up” kind of code? Hope you can help me on that.

Thanks a lot!

Every time your player collects a point, increment a variable. Only allow the button to work if their points collected == the total points in the level variable.

 public void ScenceSwitcher()
 {
     if (Player.PointsCollected == Level.TotalPoints)
     {
         SceneManager.LoadScene(2);
     }
 }