Why Apple car chargers don't show compatibility with Ipad Pro 11' (third generation)?

Your iPad Pro 11” has a USB-C port for connection of a charger via a USB cable. As with most models of iPad, yours requires a power source capable of providing at least 12W (i.e., 2.4A @5V) to reliably charge. As such, you need to identify a USB car charger that can provide at least 12W - using either a USB-C or USB Type-A connection and appropriate USB cable.

If the car charger uses the older USB Type-A connection, you’ll need a USB Type-A to USB-C cable. For example:

• mophie USB-A Cable with USB-C Connector (1 m)

https://store.apple.com/uk/xc/product/HN892ZM/A

Otherwise, if the car charger has a USB-C connection, you’ll require a USB-C to USB-C cable:

• USB-C Charge Cable (1m)

https://store.apple.com/uk/xc/product/MM093ZM/A

Apple directly market these third-party car chargers (designed for use with a standard automative 12V socket) compatible with your iPad using an appropriate cable:

• mophie USB-C Car Charger

https://store.apple.com/uk/xc/product/HN7Z2ZM/A

• mophie Dual USB-A Car Charger

https://store.apple.com/uk/xc/product/HN812ZM/A

• mophie Dual (USB-C/USB-A) Car Charger

https://store.apple.com/uk/xc/product/HN822ZM/A