How to retrieve recently deleted Notes on iPhone?

Have you checked on iCloud here:

Delete and recover notes on iCloud.com - Apple Support

This would only work if you were using iCloud to store the notes. After resetting the iPhone, all data on the device will be erased and the Notes would only be available then if they were in your backup file before the notes got erased.

At the bottom of your notes list there is the recently deleted folder... are they in there? If so, all you have to do is move them back to the notes folder.