Recovering deleted Notes on iPhone

They will remain there for 30 days unless deleted from the folder before that time.

If you're missing notes on your iPhone, iPad, or iPod touch - Apple Support

Delete and recover notes on iCloud.com - Apple Support

If it has been longer than 30 days or deleted from the recently deleted folder, they are not recoverable.

Only way that would be possible is if you had a backup before those notes were deleted. When you delete the notes from your Recently Deleted folder, you will see a warning that continuing with that actions will result in your notes being permanently deleted. Ignoring that warning without taking any steps to save those notes in another location, will do exactly as it says and the notes will be gone for good.