Can't update or restore
Hello. I have an iPod touch 7 that I have not updated for a long time. It has been working fine with software version 11.3.1 and worked with my car's audio system. Today, I finally decided to update it. So, I plugged it into my PC, opened iTunes, chose to update when asked to, but it couldn't install the update. There was an error in updating, so I was asked to restore to factory setting. I agreed to do, but I couldn't restore it as well. Now I have an iPod that I can't update or restore. What should I do? Thanks for any help in advance.
iPod, iOS 11