iPod Classic problem with reformat

Please help me!

I tried to reformat my iPod classic (7.gen) from the basic format to OS and I waited and sadly I unplugged during the process from Mac...

iPod is working, but it says that there is no space at all (both available or used). It`s not even possible to restore it in iTunes.

What can I do? Can I try to reformat it again?

Thanks a lot!