On the discover pro it has a hard drive so all maps are loaded onto that, so no dedicated SD card, so forget what you know,
To upgrade maps (I’ve not seen vw issue a software update on the net yet),
download vw software and download the update from there, (discover care?)
It should load it onto sd card
Put sd in car
On nav page press settings (bottom right)
Click on version information
Click update
You can also set up your sd card manually,