Hi YumaGal,
The easiest way to do what you are asking would be to restore the iPod nano's software, which erases all music and other content from the iPod. The process is described in this manual -
https://manuals.info.apple.com/MANUALS/0/MA629/en_US/iPod_nano_4th_gen_UserGuide .pdf
See at the bottom of page 69 -
To update or restore iPod nano:
1 Make sure you have an Internet connection and have installed the latest version of iTunes from www.apple.com/ipod/start.
2 Connect iPod nano to your computer.
3 In iTunes, select iPod nano in the source list and click the Summary tab.
The Version section tells you whether iPod nano is up to date or needs a newer version of the software.
4 Click Update to install the latest version of the software.
5 If necessary, click Restore to restore iPod nano to its original settings (this erases all data
from iPod nano). Follow the onscreen instructions to complete the restore process.
Thanks for using Apple Support Communities.
Sincerely,
Brett L