replace "OnPress" (button) by "OnMouseDown" (collider)

Hello, I got some piece of code I must say I don't understand very well. This works only on UI buttons but I need to make it work when click on a collider. How can I manage to replace it with something simple like "void OnMouseDown()" ?

 [Serializable]
     public class ButtonPressEvent : UnityEvent { } 
 
     public ButtonPressEvent OnPress = new ButtonPressEvent();
 
     public void OnPointerDown(PointerEventData eventData)
 {
         OnPress.Invoke();
     }
 

 

Thanx