Using IK to move character's hand position to pickup

I have a character and added a FullBodyBiped component from FinalIK. How can I move the character's hand down to the pickup? This is what I've tried but it just makes the whole character float to a different position.

 void PickupWeapon()
         {
             Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
 
             RaycastHit hit;
             Debug.DrawRay(ray.origin, ray.direction * 10, Color.red);
 
             if (Input.GetMouseButtonDown(0))
             {
                 if (Physics.Raycast(ray, out hit,3) == true&&hit.collider.gameObject.tag=="Pickup.Weapon")
                 {
                     weaponPickedup = hit.transform.gameObject;
                     //ik.solver.rightHandEffector.positionOffset = weaponPickedup.transform.position;
                     ik.solver.rightHandEffector.position = weaponPickedup.transform.position;
                     //weaponPickedup.transform.parent = domHand.transform;
                     //weaponPickedup.transform.position = domHand.transform.position;
                 }
             }
         }