How do I recover notes files on iPhone 11?

If you're missing notes on your iPhone, iPad, or iPod touch read this support article --> Learn what to do if you're missing a note - Apple Support

If you store your notes on iCloud, check your Recently Deleted folder:

1. Open Notes, then tap the back icon < until you see your Folders list.

2. Tap Recently Deleted and search for your note.

If you find your note in Recently Deleted or in another folder, you can move it:

1. In the Notes list, tap Edit.

2. Select the note that you want to move.

3. Tap Move, then select the folder you want to move it to.

If you use notes with another service, like Gmail or Yahoo, check the Trash folder of that account in the Mail app. If you delete a note from the Notes app, your third-party account will usually keep it in the Trash folder. To recover a note from the Trash folder, you need to copy and paste the note to a new note in the Notes app.

P.S. Charge your phone.