I then tried installing the most recent drivers ( Driver 6.3.37-3 for macOS 10.11 - 10.15) because I thought that might work with my newer Mac OS, and after installation the Wacom Preferences Pane kept saying there were no devices attached, even when my tablet was plugged in.

I realized it was probably because the supported Mac OS versions were 10.8 - 10.11 according to the Wacom Driver site and searching 'Intuos 3'. I restarted my computer a few times and still had the issue, then I un-installed and I re-installed the driver and still had the issue. When I reinstalled the latest drivers that work with Intuos 3 tablets for Mac ( Driver 6.3.15-3), the Wacom Preferences Pane kept saying there was something wrong with the driver and the computer needed to be restarted, and if the issue persisted to re-install the driver. I tried to re-install the Wacom Drivers for the tablet to troubleshoot whether this was a hardware (mouse itself) or software (drivers) problem. I noticed my Wacom Intuos 3 mouse was acting strange (clicks not always being registered). I have an old Wacom Intuos 3 tablet (with pen and mouse) that I occasionally use with my Mac (OS 10.12.6 - Sierra).

Mac os 10.12 graphic designer