Q: how do I reset my original iPod Nano ?

A Reset, restarting iPod without affecting the iPod's data, is done as described here

Learn how to reset your iPod - Apple Support  (see section iPod with a click wheel)

A Restore erases iPod, reinstalls its software, and sets it to default settings.  That is done from the iPod's Summary settings screen in iTunes, by clicking Restore button.

Use iTunes to restore your iPhone, iPad, or iPod to factory settings - Apple Support

What are you trying to do, restart it or restore it?  And what DOES happen when you try?  Explain the actual problem...

The iPod is in Recovery mode. In order to advise you further, you'd have to answer Kenichi's question about what happens when you try to restore it in iTunes...

Make sure the Hold switch (if the iPod has a click wheel) is not in the ON position.  If the buttons are not faulty, it will Reset (restart), and you should see the Apple logo on the screen.  What happens after doing a Reset?

So, it sound like you got iPod to appear in iTunes, so you can do a Restore.

Apple's advice when you get an unhelpful error message doing a Restore

If you see error 1415, 1417, 1418, 1428, 1429, 1430, 1436, or 1439 when restoring or updating an iPod in iTunes - Apple …

Do you use a Mac or Windows PC?  If Windows, which version?

You can take it to an Apple Store.  You should an appointment with the store's Genius Bar (tech support staff) using the store's web page.

https://www.apple.com/retail/

As a Mac user, if you have not already, shut down (power off) the Mac.  Disconnect all USB devices.  You can leave standard keyboard/mouse connected, if used.  Start up the Mac, run iTunes, and connect iPod to a direct USB port on the Mac.  Try doing a Restore again.