Notes missing after update

Which update are you referring to? 

1. iOS Update? Which Version? Update your iPhone, iPad, or iPod touch - Apple Support
2. Carrier Update? Contact Carrier. Update your carrier settings on your iPhone or iPad - Apple Support
3. App Update? Which App? Contact App Developer? How to contact an app developer - Apple Support
4. Apple News Update? --> Read the latest headlines in the Apple News app - Apple ...

You may get better and prompt responses if you may kindly provide the iPhone Model that you have and the iOS version if it is known to you and re-post.

Where were the Notes? Which Folder? See the Pic below