My old modem was malfunctioning and I had to get a new one. However, now my girls can't join each other's games in Minecraft PE. Their iPods are both connected to the new wifi and they can sync apps. It is only in Minecraft PE that they get the message "Server Outdated" or "Outdated Client". They spent a lot of time creating some of these worlds and are pretty devastated that they can't join together. Any ideas?
Now, I'm not really experienced in hosting servers of any sort, breed, smell or colour, but you could try re-downloading the latest server software (or the compatible version to your girls' versions assuming they arent running the latest patch).
The actual world subfolder will be among the server's files which you can simply move over to the new server folder (in the appropriate sub-folder, where ever that is), and host it there.