Lost all my notes

Are you sure you mean "Backup". Apologies if you do, but just in case...

You can synch Notes, Contacts, Calendar and Reminders across your devices. This means that if you write a new Note on any of your devices, or on iCloud.com in a browser it will appear on all your devices. Similarly, if you delete a Note (or calendar event, reminder or contact) on iCloud.com or any of your devices it will be deleted across all your devices. It is NOT a backup - it's a synchronization and working exactly as it's meant to do. If you've recently deleted Notes then at the very bottom of the Folders list there is the "recently deleted" folder where you can recover Notes deleted in the last 30 days. iCloud.com has data recovery, but only for contacts and calendar.

Hello Insane-workflows,

Thank you for reaching out to Apple Support Communities.

It appears you are referring to syncing. Here is more information on what is backed up in iCloud:

"What iCloud Backup includes

Your iPhone and iPad backups include all the information and settings stored on your device that don't already sync to iCloud.

Device settings, Home Screen layout, and app organization

When you restore from an iCloud backup, things like your device settings, your Home Screen layout, and app organization are also restored. 

Other on-device information

Any purchased Ringtones and your Visual Voicemail password (which requires the SIM card that was in use during backup) are also included in your iCloud Backup. 

Apple Watch backups 

Your Apple Watch backup is included in the backup of your iPhone or iPad.

Photos, videos, messages, and app data

If you don't use services like Messages in iCloud or iCloud Photos, the information below is stored in your iCloud Backup to ensure that it's also protected. 

iMessage, text (SMS), and MMS messages

If you haven't turned on Messages in iCloud, your messages are included in iCloud Backup. If you use Messages in iCloud, your messages automatically sync to iCloud so they aren’t included in your daily backup.

Photos and videos on your iPhone or iPad

If you haven’t turned on iCloud Photos, iCloud Backup may include photos and videos in your Photos or Camera Roll. When you use iCloud Photos, your photos and videos automatically sync to iCloud so they aren’t included in your daily backup.

App data 

iCloud Backup includes app data for the apps that you've downloaded on your device. This includes data for third-party social media apps, games, and messaging apps, as well as apps from Apple that don't sync with iCloud. 

If the app uses iCloud Drive to store data, that information is stored in iCloud instead of your iCloud Backup. "

Additional details can be found here: What does iCloud back up?

For more details on recovering deleted notes, this page should help: Delete and recover notes on iCloud.com

Hopefully this helps clear up some information.

Cheers!