MongoParseError: Invalid scheme

Question

I am working on connecting to a MongoDB Atlas database but continue to get this error:

MongoParseError: Invalid scheme, expected connection string to start with "mongodb://" or "mongodb+srv://"

I've tried hardcoding the username and password for ATLAS_URI in my .env file, as well as placing the environment variables within ATLAS_URI but continue to get the same error. Here is my .env file: ATLAS_URI = mongodb+srv://{DBUSER}:{DBPWD}@qac.mqn4ubr.mongodb.net/?retryWrites=true&w=majority

and this is what I have stored in conn.mjs & loadEnvironment.mjs:

import { MongoClient } from 'mongodb'

const connectionString = process.env.ATLAS_URI || ''
console.log(connectionString)
const client = new MongoClient(connectionString)

let conn
try {
    conn = await client.connect()
} catch(err) {
    console.log(err)
}

let db = conn.db('sample_training')


export default db

js
import dotenv from 'dotenv'
dotenv.config()

I've been following this tutorial:MERN tutorial: MongoDB,

as well as this solution:MongoParseError: Invalid scheme but nothing has fixed this.

The expectation is for the server to run on given port