npm install firestore-export-import
you can ** generate new private key ** from project settings from firebase console and paste it to serviceAccountKey.json.
node export.js <collection_name>
note: after exporting, you need to copy the json file from <firestore-export.json> into another json file as your back-up file.
node import.js import-to-firestore.json
note: import-to-firestore.json must contain the specific json file from your collection, for example: users collection etc..
i hope it helps.. happy coding <3