Q: erase and restore

If you erase your iPod and after that restore the data you previously backed up using iTunes or iCloud, you won't lose anything.

Sync your iPhone, iPad, and iPod with iTunes using USB - Apple Support

Transfer content from an iPhone, iPad, or iPod touch to a new device - Apple Support

However, if you don't have a backup, you will lose the data from your device. Before restoring, create a backup copy of your iPod as shown in the instructions above.