I need help with a script (I'm using mirror package too!)

using UnityEngine;
using Mirror;

public class NetworkManager : Mirror.NetworkManager
{
    public override void OnStartServer()
    {
        Debug.Log("Server started");
    }

    public override void OnStopServer()
    {
        Debug.Log("Server stopped");
    }

    public override void OnClientConnect(NetworkConnection conn)
    {
        base.OnClientConnect(conn); // Call base method to handle default behavior
        Debug.Log($"Client connected: {conn.connectionId}");
    }

    public override void OnClientDisconnect(NetworkConnection conn)
    {
        base.OnClientDisconnect(conn); // Call base method to handle default behavior
        Debug.Log($"Client disconnected: {conn.connectionId}");
    }

    public override void OnServerAddPlayer(NetworkConnection conn, NetworkReader extraMessageReader)
    {
        base.OnServerAddPlayer(conn, extraMessageReader); // Call base method to handle default behavior
    }
}

That was the code I got it from chat gpt I can't find a solution (I think I'm bad at coding.)
Please help.
The errors are: Assets/Scripts/NetworkManager.cs(16,26): error CS0115: 'NetworkManager.OnClientConnect(NetworkConnection)': no suitable method found to override
Assets/Scripts/NetworkManager.cs(22,26): error CS0115: 'NetworkManager.OnClientDisconnect(NetworkConnection)': no suitable method found to override

Assets/Scripts/NetworkManager.cs(28,26): error CS0115: 'NetworkManager.OnServerAddPlayer(NetworkConnection, NetworkReader)': no suitable method found to override