The build in my app cannot communicate with the REST API

So I deployed my fullstack React-Express app to Netlify and it seems like the build cannot communicate to the REST API according to the error I get:
"Unexpected token ‘<’, "<!DOCTYPE “… is not valid JSON”

The structure of the app is as follows

app
-build
-frontend
- -public
- -src
-controllers
-models
-routes
-uploads
-util
-.babelrc
-.env
-.gitignore
-app.js
-package-lock.json
-package.json
-webpack.config.json

Here is the repo link: GitHub - nusretWazowski/places: MERNStack web app for public place sharing

And link to the app on Netlify: https://place-sharing-app.netlify.app/

The app works locally with the command npm start, and it works when deployed to heroku

Netlify doesn’t run Node.js apps, which Express relies on. You need to convert your Express routes to Nelify Functions. Working example: netlify-file-browser/netlify/functions at v2 · Hrishikesh-K/netlify-file-browser · GitHub

Thank you, I will attempt this