Hi RobInFinland,
Thank you for using the Apple Support Communities! I understand you are looking for a way to sync content from iTunes for Windows with your new iPad Pro. I can help.
To connect your new iPad Pro to your Windows PC, read more about the cable required to connect here: Charge and connect with the USB-C port on the new iPad Pro - Apple Support. I know you mentioned you're looking for a way to transfer content other than using a cable, however.
You could use Wi-Fi to sync your content, however, you would need to set up syncing with iTunes using USB first: Use iTunes to sync your iPhone, iPad, or iPod with your computer - Apple Support.
When it comes to downloading your previously purchased content, you can do this by following the steps here to redownload content using the "Not on this [device]" option: Redownload apps, music, movies, TV shows, and books - Apple Support.
If you have more specific questions that are not addressed in the above articles, feel free to reply back.
Regards.