./api is the Express Server.
I am figuring out how to deploy a MERN STACK app, till then just clone this repo and run the following commands.
cd MERN-TODO-APP
npm install #installs the next.js dependencies
cd api
npm install #installs the node.js dependencies
#then
npm run dev #This runs the next.js frontend
#open another terminal
cd api
npm start #Runs the server.js file with nodemon
Then goto http://localhost:3000 and ofcourse you need to have MongoDb
installed and running in your system.