I made a game on a unit and gave an error cs0246 how to fix it?

Question

Unity

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;
using UnityEngine.SceneManagement;

public class MainMenu : MonoBehavior
{
[SerializeField] int money;
public Text moneyText;

private void Start()
{
money = PlayerPrefs.GetInt("money");
}

public void ButtonClick()
{
money++;
PlayerPrefs.SetInt("money", money);
}

public void ToAchievements()
{
SceneManager.LoadScene(1);
}

//Update is called once per frame
void Update()
{
moneyText.text = money.ToString();
}
}

Answer 1

What is CS0246?