Listening to the "Mouse Scroll Wheel"

Hello,

I need to listen to the mouse scroll view, and if the user scrolled up, increase the "Fire Power". Following is my code.

 using UnityEngine;
 using System.Collections;
 
 public class Shooter : MonoBehaviour {
     
     public Rigidbody bullet;
     public float power = 1500f;
     public float moveSpeed = 25f;
 
     
     // Update is called once per frame
     void Update () 
     {
         float h = Input.GetAxis("Horizontal") * Time.deltaTime * moveSpeed;
         float v = Input.GetAxis("Vertical") * Time.deltaTime * moveSpeed;
         
         transform.Translate(h,v,0);
         
         if(Input.GetButtonUp("Fire1"))
         {
             Rigidbody instance = Instantiate(bullet,transform.position,transform.rotation) as Rigidbody;
             
             Vector3 fwd = transform.TransformDirection(Vector3.forward);
             
             instance.AddForce(fwd*power);
         }
         else if(Input.GetButtonUp("Mouse ScrollWheel"))
         {
             power = power * 2;
         }
     
     }
 }

But, this "MouseScrollWheel" part seems not working. What am I doing wrong?

Please help.