How do i sync a brand new IPOD Classic to an old PC that has my entire library

There is no such thing as a brand new iPod Classic. They haven't been manufactured for six years.

See Sync your iPhone, iPad, or iPod using your computer - Apple Support.

tt2

Connect to your computer and sync using the advice above. If you're not able to follow the advice say where it doesn't seem to match what you see in iTunes, or Music if you have macOS 10.15 Catalina.

tt2