Javascript – Can not connect to the endpoint

I am having some problem while to connecting to end point on server.

Here is my code.

Register.jsx

 function Register() {
  const [registerUser, setRegisterUser] = useState({
    username: "",
    email: "",
    password: "",
  });
  const handleClick = async (e) => {
    try {
      e.preventDefault();
      const response = await RegisterUser(registerUser);
      // some code 
  };
}

users.js

import axios from "axios";

export const RegisterUser = async (registerUser) => {

  console.log("In RegisterUser =====> ", registerUser);
  try {
    const response = await axios.post("/api/users/register", registerUser);
    return response.data;
  } catch (error) {
    return error.response.data;
  }
};

server.jsx

const express = require("express");
const cors = require("cors");
require("dotenv").config();
const app = express();
const dbConfig = require("./Config/dbConfig");
const port = process.env.PORT || 5000;

const server = require("http").createServer(app);

const usersRoute = require("./routes/usersRoutes");

app.use(cors({ origin: "http://localhost:3000" }));

app.use("/api/users", usersRoute);

server.listen(port, () => console.log(`Server running on port ${port}`));

usersRoutes.js

const router = require("express").Router();
const User = require("../models/userModel");

// User Registration
router.post("/register", async (req, res) => {
  console.log("In /register");
  try {
    const user = await User.findOne({ email: req.body.email });
    if (user) {
      return res.send({
        success: false,
        message: "User already exists",
      });
    }
    const newUser = new User(req.body);
    await newUser.save();
    res.send({
      success: true,
      message: "User created successfully",
    });
  } catch (error) {
    res.send({
      message: error.message,
      success: false,
    });
  }
});

module.exports = router;

When i submit my registration form I want it to send it post request to the url of the api and recieve its response.But I am getting error and it seems that, there is a problem with end point.

I am getting following error for above code :

POST http://localhost:3000/api/users/register 404 (Not Found)