Move camera forward/backwards with mouse wheel

Assuming you use the old InputManager, you can place this on your Camera GameObject to get the desired behaviour.

 using UnityEngine;
 
 public class ScrollWheelMove : MonoBehaviour
 {
     public float speed = 5.0f;
 
     private void Update()
     {
         transform.Translate(Input.mouseScrollDelta.y * speed * transform.forward); 
     }
 }