The referenced script on this Behaviour is missing! please help me

public class PlayerMovement: MonoBehaviour
{
public float speed = 6f;

 Vector3 movement;
 Animator anim;
 Rigidbody playerRigidbody;
 int floorMask;
 float camRayLength = 100f;
 
 void Awake()
 {
     floorMask = LayerMask.GetMask ("Floor");
     anim = GetComponent <Animator> ();
     playerRigidbody = GetComponent<Rigidbody> ();
 }
 
 void FixedUpdate()
 {
     float h = Input.GetAxisRaw ("Horizontal");
     float v = Input.GetAxisRaw ("Vertical");
     
     Move (h, v);
     Turning ();
     Animating (h, v);
 }
 
 void Move (float h, float v)
 {
     movement.Set (h, 0f, v);
     
     movement = movement.normalized * speed * Time.deltaTime;
     
     playerRigidbody.MovePosition (transform.position + movement);
 }
 
 void Turning()
 {
     Ray camRay = Camera.main.ScreenPointToRay (Input.mousePosition);
     
     RaycastHit floorHit;
     
     if (Physics.Raycast (camRay, out floorHit, camRayLength, floorMask))
     {
         Vector3 playerToMouse = floorHit.point - transform.position;
         playerToMouse.y = 0f;
         
         Quaternion newRotation = Quaternion.LookRotation (playerToMouse);
         playerRigidbody.MoveRotation (newRotation);    
     }    
 }
 
 void Animating(float h, float v)    
 {
     bool walking = h != 0f || v != 0f;
     
     anim.SetBool ("IsWalking", walking);
 }    

}

Name the class file PlayerMovement.cs

If the script ever had a different name and was added as a component to GameObjects at that point in time those are the Gameobjects throwing the error because their component cannot find it anymore. Readd it and it should be fine