How to run an application in codesandbox with different subfolder for backend and frontend

I want to get a codesandbox for an app I am working on... The project now has two different subfolders named backend and frontend... How can that be done? I am sending for you my packages.json file content:

{
  "name": "projeto_aplicado",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "dependencies": {
    "concurrently": "^6.2.0"
  },
  "devDependencies": {},
  "scripts": {
    "server": "npm run server --prefix backend",
    "start": "concurrently \"npm run server\" \"npm run client\" ",
    "client": "npm start --prefix frontend"
  },
  "author": "",
  "license": "ISC"
}

I am also sending the link for my web app: https://codesandbox.io/s/blissful-fire-jjnl5?file=/package.json:0-393

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