as the title says - I'm trying to deploy a website to Heroku for the first time. I changed all ports to Process.env.PORT || 3001 ( 3001 is the default one ).

I'm receiving this error upon running heroku logs --tail

Also I have a procfile with the following data in it

web: node backend/index.js // server index.js is in backend folder

and here's my Package.json file

{
  "name": "marketapp",
  "version": "0.1.0",
  "private": true,
  "dependencies": {
    "@testing-library/jest-dom": "^5.16.3",
    "@testing-library/react": "^12.1.4",
    "@testing-library/user-event": "^13.5.0",
    "axios": "^0.26.1",
    "babel": "^6.23.0",
    "bootstrap": "^5.1.3",
    "cors": "^2.8.5",
    "mongoose": "^6.2.10",
    "node-cron": "^3.0.0",
    "puppeteer": "^13.5.1",
    "react": "^18.0.0",
    "react-bootstrap": "^2.2.3",
    "react-dom": "^18.0.0",
    "react-hot-loader": "^4.13.0",
    "react-router-dom": "^6.3.0",
    "react-scripts": "5.0.0",
    "web-vitals": "^2.1.4"
  },
  "scripts": {
    "start": "react-scripts start",
    "build": "react-scripts build",
    "test": "react-scripts test",
    "eject": "react-scripts eject",
    "server": "node public/index.js",
    "dev": "concurrently \"npm run server\" \"npm run start\""
  },
  "eslintConfig": {
    "extends": [
      "react-app",
      "react-app/jest"
    ]
  },
  "browserslist": {
    "production": [
      ">0.2%",
      "not dead",
      "not op_mini all"
    ],
    "development": [
      "last 1 chrome version",
      "last 1 firefox version",
      "last 1 safari version"
    ]
  },
  "devDependencies": {
    "concurrently": "^7.1.0",
    "netlify-cli": "^9.16.3",
    "nodemon": "^2.0.15"
  }
}