Updated my MacBook to OS Catalina and now can no longer see my older iPod. Did I screw up?

Where are you looking for it? Catalina splits the functions of iTunes between separate apps.

What happened to iTunes? - Apple Support

Use the Finder to sync your iPhone, iPad, or iPod touch with your Mac - Apple Support

These support articles only mention iPod Touches – the ones that run iOS. Maybe that means that iPod Touches are the only iPods that Catalina supports, or maybe it just means that Apple didn't want to mention older iPods. I would suggest trying the directions for synchronizing iPod Touches and see if those help.

This video suggests that Catalina will synchronize even with old iPods.

https://www.youtube.com/watch?v=aybDreAz6Lk