My react frontend not establishing connection with my node backend - node.js

Question

I am trying to get my react frontend to establish connection with my node backend. The node backend works when I am using PostMan. I have gone through most of the options suggested on this plateform but none is helping.
This is the Fetch request in react
import axios from 'axios'
// Sending Request to register User
let URL = "/user/"
const register = async (userData) => {
let response = await axios.post(URL + 'register', userData)
if (response.data) {
localStorage.setItem('user', JSON.stringify(response.data))
}
return register.data
}
This is my package.json file for the react:
{
"name": "frontend",
"version": "0.1.0",
"private": true,
"options": {
"allowedHosts": [
"localhost",
".localhost"
],
"proxy":"http://localhost:8000"
},
"dependencies": {
"#reduxjs/toolkit": "^1.8.6",
"#testing-library/jest-dom": "^5.16.5",
"#testing-library/react": "^13.4.0",
"#testing-library/user-event": "^14.4.3",
"axios": "^1.1.2",
"bootstrap": "^5.2.2",
"react": "^18.2.0",
"react-bootstrap": "^2.5.0",
"react-dom": "^18.2.0",
"react-icons": "^4.4.0",
"react-redux": "^8.0.4",
"react-router-dom": "^6.4.2",
"react-scripts": "5.0.1",
"react-toastify": "^9.0.8",
"web-vitals": "^2.1.4"
},
"scripts": {
"start": "react-scripts start",
"build": "react-scripts build",
"test": "react-scripts test",
"eject": "react-scripts eject"
},
"eslintConfig": {
"extends": [
"react-app",
"react-app/jest"
]
},
"browserslist": {
"production": [
">0.2%",
"not dead",
"not op_mini all"
],
"development": [
"last 1 chrome version",
"last 1 firefox version",
"last 1 safari version"
]
}
}
This is my Node index.js file to handle the post request
require('dotenv').config()
const express = require('express')
const bodyParser = require('body-parser')
const { connectToDb } = require('./database/db');
const cors = require('cors')
const port = process.env.PORT || 5000
connectToDb();
const app = express()
app.use(express.json())
app.use(bodyParser.urlencoded({extended:true}))
app.use(cors())
app.use('/user', require('./routes/userRoutes'))
app.listen(port, () => {
console.log(`Server is running on ${port}`)
})
What should am I not doing right?