Thanks for asking the Apple Support Communities for help with your Notes. You may be able to get your deleted notes back from your Recently Deleted folder.
Check out this help article: Delete a note
If they are not there or you deleted it from there also, the only option will be to restore the data from your backups. Please be aware, doing this will replace all the data on your device with the data in the backup. If you choose to go this route, ensure you have a backup of the current data in either iTunes or iCloud. If you will be restoring your data from an iCloud backup, you may want to make a new backup of the current data with iTunes. You can make a backup in iCloud or iTunes using this article: How to back up your iPhone, iPad, and iPod touch
You can restore your backup to your device using this help article: Restore your iPhone, iPad, or iPod touch from a backup
Thanks and have a nice day.