Getting what gameobject another gameobject was mousedragged to

I am trying to get my script to determine which object the gameobject I am dragging is dragged on top of. So I drag gameobject A onto gameobject B, how would I go about determining that it was gameobject B that gameobject A was dragged onto?

if your gamebjectA got colliders you can do this add a tag

void OnCollisionEnter (Collision col)
        {
            if(col.gameObject.tag == "gameObjectB")
            {
                //...
            }
        }