How to Trigger Animation After x Items Collected?

Below is my code I am working with, how can I trigger an animation once x1 items are collected?

using UnityEngine;
using System.Collections;

public class Item : MonoBehaviour
{

///////////////////////////////////////////////////////////////////////
///This file goes on a Collectable Game Object that is in your scene///
///////////////////////////////////////////////////////////////////////

//Set up variables for text output on screen, and audio
//This will create "open slots" in your editor, on the object that has this script
//You will drop in your GuiText and Audio into the open slots.
public GUIText TextOutput;
public AudioClip SoundToPlay;

//Set up variable for number of items collected.
//Each time you collect something, this can be updated to be you "inventory" of that item.
public static int itemCounter = 0;



//Code for when the player collides with an item to collect.
void OnTriggerEnter (Collider other)
{
	//When something hits the collectable, if it is the player that touches the collectable,
	//Play a noise,
	//Display some text,
	//Update the inventory,
	//Delete the prefab.
	if ((other.tag == "Player")&& (Item.itemCounter == 0)) {
		//Play the audio at the collectables position
		AudioSource.PlayClipAtPoint (SoundToPlay, this.transform.position);

		//Update the GuiText
		TextOutput.text = 
			"Coin Found";
		 	

		//Update the varible for the # of items you have in your inventory
		//The below code is a "shorthand" method of writing itemCounter = itemCounter +1;
		itemCounter += 1;
	
		//Simulate collection by destroying the prefab object
		Destroy (gameObject.transform.parent.gameObject);
	
	}

		
	
	}

}

}

Have a script on the player that keep track of the items and increase that value each you collect. Check that value to play the anim.

public class ItemOnPlayer:MonoBehaviour{
   int item;
   public int Item{
      get{return item;}
      set{
           item += value;
           if(item == 10)// Play animation
        }
   }
}

on your collision script:

if (other.tag == "Player"){
     other.gameObject.GetComponent<ItemOnPlayer>().Item++;
     // rest of code
}

You already have a counter named itemCounter in your script, so you just need to use it :
l.38

itemCounter += 1;
if(itemCounter >= numberRequired) {
    other.animation.Play ("animationName"); 
}