iPod shuffle and laptop

The 4th-generation iPod Shuffle apparently came with a special 3.5mm-to-USB-A cable to be used for charging it, and loading it with music from a computer. I assume you still have that cable. It sounds like your MacBook Air has USB-C (Thunderbolt) ports and no USB-A ports. So the special cable won't plug directly into your computer.

That's easy to fix. There are all sorts of ways to attach USB-A devices to USB-C ports, using anything from plug adapters to hubs to docks. If you get a basic plug adapter or cable, look for one that has a USB-C plug, a USB-A socket, and whose description explicitly says that it supports BOTH power and data transfer.

https://www.amazon.com/s?k=usb-a+to+usb-c+adapter

The other thing you'll come across is that your version of macOS doesn't support iTunes. Apple replaced iTunes with separate built-in applications a few versions of macOS ago. Now you will use the Music app to manage your music library, and the Finder to manage synchronization of that library with your iPod Shuffle.

What happened to iTunes? - Apple Support

(I am assuming that Apple has not removed support for iPod Shuffles, but has just relocated it, the way that they relocated most of the stuff in iTunes.)

Note: I just found this potential "gotcha":

This thread suggests that if you have enabled the "Disk Mode" feature on an iPod Shuffle, you will need to disable that feature, using an older Macintosh (pre-Catalina) or Windows PC, before a newer Mac will synchronize with the Shuffle.

How do I sync my iPod shuffle using Apple… - Apple Community