When you turned off that option you were given the following screen:
What you wanted to do at that point was to select Go to Notes so that you could then select "EDIT" which would provide you with an option to "Move" the selected Notes to iCloud.
Unfortunately, by deleting them, they were completely wiped.
You can try to see if they might be in a backup. iCloud-sync'd notes do not go to your backup, of course, but local iPhone Notes might. Do you have a backup that you created prior to the Delete action?
Cheers,
GB