drawing an arrow to help the user shots the enemy

Doing 2D game side scroll, the character able to pick up stuff and throw it on the enemy by using the mouse left click with pointing on the enemy, i need to draw an arrow following the mouse position ?

private Vector3 screenPoint;

private Vector3 offset;

private float throwSpeed = 6f;

public void ThrowPickup()

{
	if(throwSound)
	{
		audio.volume = 1;
		audio.clip = throwSound;
		audio.Play ();
	}
	Destroy (joint);
	
	heldObj.rigidbody.interpolation = objectDefInterpolation;
	heldObj.rigidbody.mass /= weightChange;

	screenPoint = Camera.main.WorldToScreenPoint(gameObject.transform.position);
	offset = Camera.main.ScreenToWorldPoint(new Vector3(Input.mousePosition.x, Input.mousePosition.y, screenPoint.z)) - gameObject.transform.position;

	float XInc = offset.x * throwSpeed;
	float YInc = offset.y * throwSpeed;
	
	heldObj.rigidbody.velocity += new Vector3(XInc, YInc, 0);
			
	heldObj = null;
	timeOfThrow = Time.time;
	
}

i need to draw an arrow following the mouse position ?

So it seems you are doing 3D side scrolling. Check these documents: