I'm not sure what "(6)" and "(8)" are supposed to mean in terms of models. However, since you're running Sequoia and Sonoma, my guess is that both of your Macs are recent enough that they have USB-C (Thunderbolt) ports, and do not have USB-A ports.
If you buy an external drive that comes with a USB-A cable, there are lots of ways to bridge the difference between USB-A and USB-C. E.g.,
- Adapters
- Hubs/docks with USB-A ports
- Replacing a portable drive's USB-A to USB 3.0 Micro B cable with a USB-C to USB 3.0 Micro B one.