Unable to set Environment variable from Powershell or Windows

[saamalam]

As per the instruction

Setup your MongoDB connection: $ export MONGORILLA_MONGO_URL="mongodb://localhost/my_mongorilla"

trying to do the same on Windows for MLab with: $ set MONGORILLA_MONGO_URL="mongodb://localhost/my_mongorilla"

and then running the npm run start or node server.js

output this error:
Loading config file... undefined
Impossible to connect to MongoDB.

I also tried it by using dotenv package and insert the variable MONGORILLA_MONGO_URL="mongodb://localhost/my_mongorilla" none works