Try to load your latest iCloud backup or computer backup (whichever you chose to do) before you deleted the notes. This should recover your OR if you are using iOS 9 or 10. You should be able to get the notes back from "Recently Deleted" section.
Just additional but if you have a Mac did you check the notes in that? Just make sure it's not connected to the interent (turn off Wifi or unplug the ethernet) if it hasn't synced to iCloud since you deleted your notes they should still be a local copy. The same for an iPad, again make sure the internet is off. You can also try going to www.icloud.com it's a last ditch effort.