Node.js, Express.js, Angular.js: Hosting my own API

I am new to coding and I have a question about a small app that I created with angular.js that makes a post request to another express.js app. It's a simple parentheses balance checker, you can find the whole code here: https://github.com/OGsoundFX/parentheseschecker

The FrontEnd-Refactored folder contains the Angular.js app and the APItesting contains the express.js API.

The app is working, but I have only been using it locally. The API runs on localhost:3000 and the app on localhost:8080

But what if I want to make it public? How would I go about it? I don't really know where to start. Where to host a node.js of express.js app. I read about AWS, would that be good, or are there better services?

I have a Wordpress website hosted on https://www.mddhosting.com/ but that wouldn't work, right?

My Angular app is calling the api locally at the moment, so I will probably have to change the API link that it is fetching:

ApiService.js

function ApiService($http) {
    API = '//localhost:3000/parentheses';
    this.getUser = (entry) => {
        return $http
            .post(API, { string: entry} )
            .then(function (response) {
                return response.data;
            }, function (reason) {
                // error
            })
    };
};

angular
    .module('app')
    .service('ApiService', ApiService);

In my API server.js

const http = require('http');
const app = require('./app')

const port = process.env.PORT || 3000;

const server = http.createServer(app);
server.listen(port);

I will definitely have to change API = '//localhost:3000/parentheses'; in my AngularJS app, but should I change const port = process.env.PORT || 3000; ?

I just need a little push start to help me clear some confusion. Thanks!