Assigned variable

Hi I can figure out what is wrong on this script:

 using UnityEngine;
 using System.Collections;
 
 public class Shooter : MonoBehaviour {
     
     public Rigidbody bullet;
     public float power = 1500f;
     public float moveSpeed = 2f;
 
     
     void Update () {
         
         float h = Input.GetAxis("Horizontal") * Time.deltaTime * moveSpeed;
         float v = Input.GetAxis("Vertical") * Time.deltaTime * moveSpeed;
         transform.Translate(h, v, 0);
 
         
         if(Input.GetButtonUp("Fire1"))
         {
             
             Rigidbody instance = Instantiate(bullet, transform.position, transform.rotation)as Rigidbody;
             Vector3 fwd = transform.TransformDirection(Vector3.forward);
             instance.AddForce(fwd * power);
             
         }
     }
 }

I geting this:

UnassignedReferenceException: The variable bullet of Shooter has not been assigned.

You probably need to assign the bullet variable of the Shooter script in the inspector. UnityEngine.Object.Internal_InstantiateSingle (UnityEngine.Object data, Vector3 pos, Quaternion rot) (at C:/BuildAgent/work/d63dfc6385190b60/artifacts/EditorGenerated/UnityEngineObject.cs:74) UnityEngine.Object.Instantiate (UnityEngine.Object original, Vector3 position, Quaternion rotation) (at C:/BuildAgent/work/d63dfc6385190b60/artifacts/EditorGenerated/UnityEngineObject.cs:84) Shooter.Update () (at Assets/Shooter.cs:21)