Hello PilotPete,
Unfortunately there is no such possibility to upgrade firmware while using the MacOS machine.
Firmware update can be only done while using the Windows machine. In order to do so, you will need to plug in your D6000 to the Windows laptop and download -> install firmware upgrade.
Please remember to have only the dock plugged in, without any monitors/usb devices plugged in to the dock.
Afterwards, you will be able to connect the D6000 to your MacOS laptop.
Kind regards,
Jakub