node serving endpoint configuration

I've learned to develop a react app with node.

At the moment, when i put yarn start in the terminal, the server is available at http://localhost:3000/.

I would like to serve it at http://localhost:3001/app

That means changing the port and the endpoint...How can i do that?

This is the content of my package.json :

{
  "name": "confusion",
  "version": "0.1.0",
  "private": true,
  "dependencies": {
    "@testing-library/jest-dom": "^5.16.4",
    "@testing-library/react": "^13.1.1",
    "@testing-library/user-event": "^13.5.0",
    "bootstrap": "5",
    "bootstrap-social": "^5.1.1",
    "cross-fetch": "^3.1.5",
    "font-awesome": "^4.7.0",
    "react": "^18.0.0",
    "react-dom": "^18.0.0",
    "react-redux": "^8.0.1",
    "react-redux-form": "^1.16.14",
    "react-router-dom": "^6.3.0",
    "react-scripts": "5.0.1",
    "reactstrap": "^9.0.2",
    "redux": "^4.2.0",
    "redux-logger": "^3.0.6",
    "redux-thunk": "^2.4.1",
    "web-vitals": "^2.1.4"
  },
  "scripts": {
    "start": "react-scripts start",
    "build": "react-scripts build",
    "test": "react-scripts test",
    "eject": "react-scripts eject"
  },
  "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"
    ]
  }
}

thank you