I have a realm that has run out of time, but I had it in single player, and now it won't show up. It is still in saves, and in the folder in still has
level.dat and the region folder. How can I fix this?
Normally you should be able to export your realm even if your subscription has shortly ended. Maybe you try a re-download and use it again.
You can read more about it in the Realm FAQ.
Can I export my Minecraft map from Realms?
You can export your maps at any time, even for a limited duration after your subscription has expired.