MyCollisionDetector.cs

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

public class MyCollisionDetector : MonoBehaviour
{
    public GameObject panel;
    public Transform playerObject;

    public float distance = 2;
    // Start is called before the first frame update
    void Start()
    {

    }

    // Update is called once per frame
    void Update()
    {
        //Debug.LogError("Hello");
    }
    void OnMouseDown()
    {
        var dist = Math.Abs(Vector3.Distance(this.transform.position, playerObject.position));
        Debug.Log("Distance is " + dist);

        if (dist < distance){
            Destroy(gameObject);
            panel.SetActive(true);
            var conteggio = GameObject.Find("Player").GetComponent<Conteggio>();
            conteggio.checkObjects();
        }
    }

}