I got URI not defined error while trying to connect database

.env file
MANGO_URI = mongodb+srv://revathi:aprilchrisoula@mern1.jxvzdqi.mongodb.net/?retryWrites=true&w=majority
PORT= 5000
NODE_ENV=development
server.js 
const express = require("express");
const  dotenv = require("dotenv");
const connectDB = require("./config/db.js");
const mongoose = require("mongoose");


dotenv.config();

const app = express();


connectDB();

mongoose.set('strictQuery', false);
mongoose.set('strictQuery', true);
mongoose.connect()


app.get("/",(req,res) => {
	res.send('get request is sending on port ${PORT}');
});

app.post("/item",(req,res) => {
	res.send('post request is sending on port ${PORT}');
});

app.put("/newItem",(req,res) => {
	res.send('put request is sending on port ${PORT}');
});

app.delete("/newItem",(req,res) => {
	res.send('delete request is sending on port ${PORT}');
});

const PORT = process.env.PORT || 5000;


app.listen(
	PORT,
	console.log(`Server running in ${process.env.NODE_ENV} mode on port ${PORT}`)
);

What does db.js look like?

(post deleted by author)

If you do not import dotenv, then this will be undefined.

Your environment variable looks a little too fruity.
Also you’re sharing your username and password, which is never wise!