How to get this subcollection’s ref id in firestore

I am trying to get this subcollection’s ref id
[1]: https://i.stack.imgur.com/4Ato6.png
I am following this tutorial however :
[2]: https://www.pluralsight.com/guides/consume-data-from-firebase-firestore-in-a-react-app
I want to get the hBYWvZ3KN3NLLrucTpryeTQZnHz2 from the firestore :

 const HighlightDbId =  await db.collection('highlights').doc('2SCS2S0JnzngWEiYkHNk').collection('hBYWvZ3KN3NLLrucTpryeTQZnHz2')

Please how can I possible get that id ??