Q: Can't get my notes back

See this similar themed thread -- How can I recover iCloud deleted notes?

If the notes are on iCloud, you should be able to access them at iCloud.com > notes via your computers browser. I'm not sure what you have done, but you can't delete the mail app, if you turned mail and notes of in your iCloud settings, that will only remove the data from your device, not from iCloud.

If the Notes aren't available or visible (via the Notes app at icloud.com) then you may be looking at the unfortunate possibility that the data is irretrievably gone.