Can I charge my iPad Pro with usb-c cable to usb charger in my car

Your iPad requires at least 10-12W (2.0-2.4A @5V) to reliably charge. If the USB outlet can provide adequate power, then yes, you can do so.

Be aware that many car USB connectors are primarily intended to provide a connection to the vehicle infotainment system - and are not necessarily designed to provide charging-power to high demand devices such as iPad.

If your car has a regular 12V outlet, you may achieve significantly better charging if you purchase a USB-C PD (Power Delivery) auto-charger - and connect your iPad via a USB-C to USB-C cable. This has the capability, subject to the charger rating, of charging your iPad Pro at its maximum supported charging rate - 18W (2A @9V / 1.5A @12V).

Here is one example marketed by Apple - manufactured by Anker:

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

https://store.apple.com/uk/xc/product/HN822ZM/A//:0