Whats wrong with my score script

I have been using this score system script without any problem in 3d. But when I tried to modify this script for my 2d game I am getting this error Script Error: OnCollisionEnter2D .

I dont know whats wrong with my code but I just need little help at here.

My 3d score code(Not Working)

     var score = 0;
      
     function OnTriggerEnter( other : Collider ) {
     if (other.tag == "Coin") {
     score += 1;
     Destroy(other.gameObject);
     }
     }
    function OnGUI () {
 
         GUI.Label (Rect (20, 20, 200, 40), score + "");
 
     }

My 2D score code(Not Working)

     var point = 0;
      
     function OnCollisionEnter2D( other : Collider  ) {
     
     if (other.tag == "Point") {
     point += 1;
     Destroy(other.gameObject);
     }
     }
     
    function OnGUI () {
 
         GUI.Label (Rect (70, 70, 200, 40), point + "");
 
     }
     
 

Can someone tell me whats wrong with my 2d code?