Script has no Raycast Manager variable

I am new to Unity and have no coding experience.

I am following this AR manual: Placing and Manipulating Objects in AR - Unity Learn

I am stuck on step 13:
Drag the SpawnableObject Prefab from the Project window into the Spawnable Prefab variable (figure 12)

I don’t have the ‘Raycast Manager’ and ‘Spawnable Prefab’ variables in my Inspector window under the Spawnable Manager (script).

This is the code in the file:

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using unityengine.xr.arfoundation;

public class SpawnableManager : MonoBehaviour
{
    [SerializeField]
    ARRaycastManager m_RaycastManager;
    List<ARRaycastHit> m_Hits = new List<ARRaycastHit>();
    [SerializeField]
    GameObject spawnablePrefab;
   
    Camera arCam;
    GameObject spawnedObject;

    // Start is called before the first frame update
    void Start()
    {
        spawnedObject = null;
        arCam = GameObject.Find("AR Camera").GetComponent<Camera>();
    }

    // Update is called once per frame
    void Update()
    {
        if (Input.touchCount == 0)
            return;

    RaycastHit hit;
    Ray ray = arCam.ScreenPointToRay(Input.GetTouch(0).position);
        if (m_RaycastManager.Raycast(Input.GetTouch(0).position, m_Hits))
    {
            if(Input.GetTouch(0).phase == TouchPhase.Began && spawnedObject == null)
            {
            if (Physics.(ray, out hit))
            {

                if (hit.collider.gameObject.tag == "Spawnable")
                {
                spawnedObject = hit.collider.gameObject;
            }
            else
            {
                SpawnPrefab(m_Hits[0].pose.position);
            }
            }
        }
        else if(Input.GetTouch(0).phase == TouchPhase.Moved && spawnedObject != null)
         {
            spawnedObject.transform.position = m_Hits[0].pose.position;
        }
        if(Input.GetTouch(0).phase == TouchPhase.Ended)
        {
            spawnedObject = null;
            }
    }
    }
   
    private void SpawnPrefab(Vector3 spawnPosition)
    {
    spawnedObject = Instantiate(spawnablePrefab, spawnPosition, Quaternion.identity);
    }
}

Our Sample scenes might be a good place to start: GitHub - Unity-Technologies/arfoundation-samples: Example content for Unity projects based on AR Foundation