[SOLVE] 2D Space shooter - explosion power-up scripting, please help!

I’m making a 2D space shooter and want to have a power-up system.

**Edit : I know my script is wrong, I want the player to trigger the power-up, and the power-up only affects the gameObjects tag with Enemy, as I want to delete everything that is collides/inside the explosion prefab when it triggers, I also want this to occur for at least 5 seconds.
I hope this edit clear things up
**

I want that if my player collides with the gameObject, it will create an explosion that will destroy all the enemies that enters it and all that was already inside it.

I have this right now

using UnityEngine;
using System.Collections;

public class FusionPowerUp : MonoBehaviour 
{
 public GameObject fusPrefab;

	void OnTriggerEnter(Collider otherObject)
    {
        if(otherObject.tag == "Player")
        {
         var expPrefab = Instantiate(fusPrefab, this.transform.position, Quaternion.identity);


//Destroy(gameObject.tag = "Enemy"); // not working
Destroy(expPrefab, 2f);
Destroy(this.gameObject);
        }
}

}

So right now when my player hits the object, it shows the explosion prefab, but thats all I’ve got. Also how do I allow my player to go pass this object, as right now the expPrefab collider doesn’t allow my player to pass through it.

Also about scoring, how do I check when an enemy dies from the explosion and add it to my score? Right now I can add score when I shoot something with my bullet collider, but with this power-up it could destroy more than one enemy at a time.

Please help!

Thank you very much

This is just brainstorming.
Have a Sphere collider for power up object. Check it isTrigger on inspector screen and when the player enters, have a boolean playerEntered that becomes true.

Then you can destroy power up object in, let’s say, 2 seconds. When that boolean is true you can do something like this:

void OnTriggerEnter(Collider otherObject)
    {
        if(otherObject.tag == "Player")
        {
              playerEntered = true;
              var expPrefab = Instantiate(fusPrefab, this.transform.position, Quaternion.identity);
              Destroy(expPrefab, 2f);
              Destroy(this.gameObject, 1.2f);
        }
}

void OnTriggerStay(Collider otherObject)
    {
        if(otherObject.tag == "Enemy" && playerEntered)
        {
              Destroy( otherObject);
        }
    }