I get issue's when i'm to try get data API

in this my code display from api:

import 'package:flutter/material.dart';
import 'package:get_api/model/model.dart';
import 'package:get_api/services/service.dart';

class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  List<User> users = [];
  bool isLoading = false;

  @override
  void initState() {
    super.initState();
    getUsers();
  }

  getUsers() async {
    setState(() {
      isLoading = true;
    });
    List<User> data = await UserService.getUsers();
    setState(() {
      users = data;
      isLoading = false;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Get API'),
      ),
      body: isLoading
          ? Center(
              child: CircularProgressIndicator(),
            )
          : ListView.builder(
              itemCount: users.length,
              itemBuilder: (context, index) {
                return ListTile(
                  title: Text(users[index].email),
                  subtitle: Text(users[index].first_name),
                );
              },
            ),
    );
  }
}

service code:

class Model User:

and then it's my link API https://reqres.in/api/users?page=2

what's wrong with my code? did i forget something step?