MyScript.cs

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

public class MyScript : MonoBehaviour
{
    [SerializeField] GameObject item;
    // Start is called before the first frame update
    void Start()
    {
        
    }

    // Update is called once per frame
    void Update()
    {
        
    }

    public void OnMouseDown()
    {
        print("call");
        item.SetActive(true);
    }
}