changing subfolder to sub-domain

I built a site in a folder off my main domain. After it was what I wanted I went to my hosting cpanel and told that folder to be a sub-domain. So it went from https://wwmgmt.org/jeff to https://jeff.wwmgmt.org I know there are those who will try the old url of https://wwmgmt.org/jeff and when they do it comes up saying page not found.
Any ideas how to fix that?
I looked at redirects but the folder name is the same one the sub-domain uses. Maybe change the name of the folder? I do not understand if they go directly to the folder why it shouldn’t work as before and then start showing the new url of jeff.wwmgmt.org….