Namespace problem. What to do?

I am following this tutorial: (2) ADVANCED 3D DASH ABILITY in 11 MINUTES - Unity Tutorial - YouTube . it says

Assets\Dashing.cs(11,13): error CS0246: The type or namespace name ‘ThirdPersonMovementDashing’ could not be found (are you missing a using directive or an assembly reference?)

What do I do?

Here is my code:

using System.Collections.Generic;
using UnityEngine;

public class Dashing : MonoBehaviour
{
    [Header("References")]
    public Transform Orientaiton;
    public Transform PlayerCam;
    private Rigidbody rb;
    private ThirdPersonMovementDashing pm;
    [Header("Dashing")]
    public float dashForce;
    public float dashUpwardForce;
    public float dashDuration;

    [Header("Cooldown")]
    public float dashCd;
    public float dashCdTimer;
    [Header("Input")]
    public KeyCode dashKey = KeyCode.E;

    private void Start() 
    {
        rb = GetComponent<Rigidbody>();
        pm = GetComponent<PlayerMovementDashing>();
    }

    private void Update()
    {
        if(Input.GetKeyDown(dashKey));
    }

    private void Dash()
    {
        Vector3 forceToApply = orientation.forward * dashForce + orientation.up * dashUpwardForce;
        
        rb.AddForce(forceToApply. ForceMode.Impulse);

        Invoke(nameof(ResetDash), dashDuration);
    }

    private void ResetDash()
    {

    }

}

As they say in the video:

and your player movement script

That variable is meant to refer to your movement script. If you don’t have one, as they also say, download and use theirs.

If something “could not be found” that either means you haven’t included a namespace, or it doesn’t exist. In the case of something called “ThirdPersonMovementDashing” where the tutorial creator is saying “your … script” when they talk about it, it’s not going to be the case that there’s a missing namespace. It just doesn’t exist.