Slider Not Working

Hi...

I am customizing my Survival Shooter and I want to insert a Slider that fills 10 points everytime an Enemy dies until 100 points. I copied the UI instructions of my HealthSlider watching the Tutorials, but it doesn't work. I tried to set my variable ShootSlider, but when I drag my ShootSlider into my script, I can't drop this inside the ShootSlider variable.

I implement my EnemyHealth code and there is my result:

using UnityEngine; using UnityEngine.UI;

public class EnemyHealth : MonoBehaviour { public int startingHealth = 100; public int currentHealth; public Slider shootSlider; public int superPower = 10; public float sinkSpeed = 2.5f; public int scoreValue = 10; public AudioClip deathClip;

 Animator anim;
 AudioSource enemyAudio;
 ParticleSystem hitParticles;
 CapsuleCollider capsuleCollider;
 bool isDead;
 bool isSinking;


 void Awake ()
 {
     anim = GetComponent <Animator> ();
     enemyAudio = GetComponent <AudioSource> ();
     hitParticles = GetComponentInChildren <ParticleSystem> ();
     capsuleCollider = GetComponent <CapsuleCollider> ();

     currentHealth = startingHealth;
 }


 void Update ()
 {
     if(isSinking)
     {
         transform.Translate (-Vector3.up * sinkSpeed * Time.deltaTime);
     }
 }


 public void TakeDamage (int amount, Vector3 hitPoint)
 {
     if(isDead)
         return;

     enemyAudio.Play ();

     currentHealth -= amount;
                 
     hitParticles.transform.position = hitPoint;
     hitParticles.Play();

     if (currentHealth <= 0) {
         Death ();
     }

     shootSlider.value += superPower;

 }

 void Death ()
 {
     isDead = true;

     capsuleCollider.isTrigger = true;

     anim.SetTrigger ("Dead");

     enemyAudio.clip = deathClip;
     enemyAudio.Play ();
 }


 public void StartSinking ()
 {
     GetComponent <NavMeshAgent> ().enabled = false;
     GetComponent <Rigidbody> ().isKinematic = true;
     isSinking = true;
     ScoreManager.score += scoreValue;
     Destroy (gameObject, 2f);
 }

}

Thanks guys! I'm newbie but I really want to learn.