projectile to cursor for a side scrolling shooter

I have a game project due, it is my final and our time frame is 9 days; which isnt that bad considering that I have a small scope for my game. The only hang up that I have run into is getting my character which does shoot, to be able to aim up and down on the y axis as the player moves along the x. A classmate told me about usinga Plane Collider in the background , set up a Vector 3 that calculates xyz but it has all gone over my head! I am an art guy by nature, drawing, modeling work, texturing is what I am most proficient so wrapping my head around code is an arguous task for me.... This is the code in which I am currently using to fire bullets:

 var myCamera : Transform;
 var prefab : Transform;
 var player : GameObject;
 // point of origin for particles
 var flashpoint: Transform;
 // actually particles
 var muzzleFlash: GameObject;
 var otherClip : AudioClip;
 
 function Update () 
 {
         if(Input.GetButtonDown("Fire1"))
         {
             Instantiate(muzzleFlash, flashpoint.transform.position, flashpoint.transform.rotation);
             var myBullet = Instantiate(prefab, myCamera.transform.position, myCamera.transform.rotation);
             //this tells the ingine to ignore detection of coliders between bujllet and player
             Physics.IgnoreCollision(player.collider, myBullet.collider);
             myBullet.rigidbody.AddForce(myBullet.transform.forward * 5000);
             if (!audio.isPlaying)
             {
                 audio.clip = otherClip;
                 audio.Play();
             }
         }
 }

and this is some code I found that does what I want apparently, only I do not have the slightest as how to impliment it into my game or if it is c# or javascript syntax:

 // Find the difference vector pointing from the weapon to the cursor
 Vector3 diff = cursor.transform.position - weapon.transform.position;
 // Always normalize the difference vector before using Atan2 function
 diff.Normalize();
 
 // calculate the Z rotation angle using atan2   
 // Atan2 will give you an angle in radians, so you
 // must use Rad2Deg constant to convert it to degrees
 float rotZ = Mathf.Atan2(diff.y,diff.x) * Mathf.Rad2Deg;
 
 // now assign the roation using Euler angle function
 weapon.rotation = Quaternion.Euler(0f,0f,rotZ);