• Make sure both Firebase Realtime Database and Firestore are turned on in the Firebase console.
• Head over to the Firebase console.
• Pick your project.
• If Firestore isn't enabled yet, go to Firestore Database and click “Create database.”

• Install the Firebase SDKs in your development environment.

npm install firebase

• Set up Firebase in your app.

import firebase from "firebase/app";
import "firebase/database";
import "firebase/firestore";

// Your web app's Firebase configuration
const firebaseConfig = {
  apiKey: "YOUR_API_KEY",
  authDomain: "YOUR_AUTH_DOMAIN",
  databaseURL: "YOUR_DATABASE_URL",
  projectId: "YOUR_PROJECT_ID",
  storageBucket: "YOUR_STORAGE_BUCKET",
  messagingSenderId: "YOUR_MESSAGING_SENDER_ID",
  appId: "YOUR_APP_ID"
};

// Initialize Firebase
firebase.initializeApp(firebaseConfig);
const db = firebase.database();
const firestore = firebase.firestore();

• Create a function to read data from Firebase Realtime Database.

async function readFromRealtimeDatabase() {
  const snapshot = await db.ref('/').once('value');
  return snapshot.val();
}

• Create a function to write data to Firestore.

async function writeToFirestore(data) {
  const batch = firestore.batch();
  
  Object.keys(data).forEach(key => {
    const ref = firestore.collection('your-collection').doc(key);
    batch.set(ref, data[key]);
  });
  
  await batch.commit();
}

• Combine the read and write functions to migrate the data.

async function migrateData() {
  const data = await readFromRealtimeDatabase();
  await writeToFirestore(data);
}

migrateData().then(() => console.log("Data migration completed!"));

• Check your Firestore database in the Firebase console to make sure the data has been successfully migrated.

• Change your app's database interaction logic to use Firestore instead of Firebase Realtime Database.

// Example for reading data from Firestore
firestore.collection('your-collection').get()
  .then(querySnapshot => {
    querySnapshot.forEach(doc => {
      console.log(doc.id, " => ", doc.data());
    });
  });

• Once you've verified the migration and updated your app logic, remove any remaining Firebase Realtime Database references from your codebase.