Setting an object from a pool active not working

Hi,

I am trying to pull one of my "Explosion" Prefabs from an object pool that was instantiated at start and set it to active when my player runs into my dynamite character. But for some reason I can't get it to work. I have tried two different ways. Here is the first version of my script for the first way:

 using UnityEngine;
 using System.Collections;
 
 public class DynaDerpExplode : MonoBehaviour 
 {
 
     private GameObject explosionPrefab;
     private PlayerHealth playerHealth;
     public int damage = 2;
     private GameObject objectPool;
 
     // Use this for initialization
     void Start () 
     {
         objectPool = GameObject.Find ("ObjectPool");
         explosionPrefab = objectPool.GetComponentInChildren<Explosion>();
     }
     
     // Update is called once per frame
     void OnTriggerEnter2D(Collider2D other) 
     {
         if(other.gameObject.tag == "Player")
         {
             Explode();
             other.gameObject.GetComponent<PlayerHealth>().playerCurHp -= damage;
         }
     }
 
     void Explode()
     {
         explosionPrefab.transform.position = gameObject.transform.position;
         explosionPrefab.SetActive(true);
         gameObject.SetActive(false);
 
     }
 }

But I get this error:

cs(16,69): error CS0246: The type or namespace name `Explosion' could not be found. Are you missing a using directive or an assembly reference?

Then I tried this as my second attempt:

 using UnityEngine;
 using System.Collections;
 
 public class DynaDerpExplode : MonoBehaviour 
 {
 
     private GameObject explosionPrefab;
     private PlayerHealth playerHealth;
     public int damage = 2;
 
     // Use this for initialization
     void Start () 
     {
         
     }
     
     // Update is called once per frame
     void OnTriggerEnter2D(Collider2D other) 
     {
         if(other.gameObject.tag == "Player")
         {
             Explode();
             other.gameObject.GetComponent<PlayerHealth>().playerCurHp -= damage;
         }
     }
 
     void Explode()
     {
         explosionPrefab.transform.position = gameObject.transform.position;
         explosionPrefab.SetActive(true);
         gameObject.SetActive(false);
 
     }
 }

But I get a null reference exception when the player hits the dynamite character and it points to this line:

 explosionPrefab.transform.position = gameObject.transform.position;

If anyone has an idea of what I can do to get this to work please let me know, thanks!