how do i move objects with the mouse

hi i am new with unity and I making a board game but i need to move a game object with the mouse in gameplay for a point a to b how do i do that

See this question:

var distance_to_screen : float;
var pos_move : Vector3;

function OnMouseDrag()
	distance_to_screen = Camera.main.WorldToScreenPoint(gameObject.transform.position).z;
	pos_move = Camera.main.ScreenToWorldPoint(new Vector3(Input.mousePosition.x, Input.mousePosition.y, distance_to_screen ));
	transform.position = new Vector3( pos_move.x, pos_move.y, pos_move.z );