hi, Chromecaster, my suggestion is that the Apple CD drive requires more power than then the Belkin multi-port adapter can provide....would this one be it ?? https://www.belkin.com/us/docks-hubs/usb-c-docks/connect-usb-c-6-in-1-multiport-adapter/p/p-avc008/.... if so, it's a hub, which is fine, unless you're trying to use something that requires more power than the hub can deliver.... then that thing won't work.... what you want is an active powered dock...... or to plug the Apple CD drive directly into your iMac....
it has a USB-A cable permanently attached to it, so a USB-A (female) to USB-C (male) adapter /cable would work fine....
john B