How to find one object in specific layer?

Post a shot with scene Hierarchy please.

You shouldn't use FIND function. One valid procedure is:

On Start() of these objects, they call a method REGISTER(object) on another class (controller). objects are added to a list or dictionary. On Destroy you can DEREGISTER

When you need to check object proprieties, use the list. If you need to filter by layer, you may use a dictionary

By the way, using unity tools, you can use GameObject.FindGameObjectsWithTag

 using UnityEngine;
 using System.Collections;
 
 public class ExampleClass : MonoBehaviour {
     public GameObject respawnPrefab;
     GameObject[] respawns;
     void Start() {
             respawns = GameObject.FindGameObjectsWithTag("Respawn");
         
         foreach (GameObject respawn in respawns) {
             if(respawn.layer == 0)
             Instantiate(respawnPrefab, respawn.transform.position, respawn.transform.rotation) as GameObject;
         }
     }
 }