Error ITrackableEventHandler

hello dears

I am trying to create the following scripts, with the ITrackableEventHandler, but it shows error CS0246 "Assets\Scripts\ShipRecoScript.cs(6,46): error CS0246: The type or namespace name 'ITrackableEventHandler' could not be found (are you missing a using directive or an assembly reference?)".

Version Unity: 2019.3.9f1 (64-bit) Vuforia version: 9.1.7

using System.Collections;

using System.Collections.Generic;

using UnityEngine;

using Vuforia;

public class ShipRecoScript: MonoBehavior, ITrackableEventHandler

{

    private TrackableBehavior mTrackableBehavior;

    void Start ()

    {

        mTrackableBehaviour = GetComponent <TrackableBehaviour> ();

        if (mTrackableBehaviour)

        {

            mTrackableBehaviour.RegisterTrackableEventHandler (this);

        }

    }

    public void OnTrackableStateChanged (

                                    TrackableBehaviour.Status previousStatus,

                                    TrackableBehaviour.Status newStatus)

    {

        if (newStatus == TrackableBehaviour.Status.DETECTED ||

            newStatus == TrackableBehaviour.Status.TRACKED ||

            newStatus == TrackableBehaviour.Status.EXTENDED_TRACKED)

        {

            // move the boat

            // Debug.Log ("move");

            MoveScript.current.MoveShip ();

        }

        else

        {

            // return the boat to its place

            MoveScript.current.ResetShip ();

            // Debug.Log ("return");

        }

    }

}