Phantom-1 is correct, you should be able to see what default email account you are using on your iPhone or iPad. I have 2 email accounts set up, but Yahoo is the default account where my notes are synced. Even though my 2nd account is not set up as the default, there is a notes folder in that email account. It's empty, because as I said, it's not the default account, but the folder is there.
If you check your email account, and there is no notes folder, then you probably need to go to settings/mail, contacts/calendars. Choose the email account and check to see if notes is turned on. If not, turn it on, and your notes should sync to that account.
Hope this helps....