How can you sync 2 iPad Pro without a computer

You can do an iCloud backup of all information you want transferred/shared between each device logged into your iCloud account. To do this, click on your name (next to your picture/icon) in Settings>iCloud and adjust any apps that you'd want to share information between devices by selecting to them to use iCloud or not.

There's also the option to use iTunes Wi-Fi Sync, but you would need to connect to iTunes initially to set it up.

Do an iCloud or iTines backup.

Backups – Choose Method

Back up your iPhone, iPad, and iPod touch

and then restore it to the other iPad. Then Settings/Your Name/iCloud and turn on desired syncing.

Backup - Restore your device from an iCloud or iTunes backup

Ah, sorry I left that out! All you need to do is login with your iCloud account in Settings. If you want to remove all info/pictures/everything currently on it, do a reset by going to Settings>General>Reset (at the bottom) and Erase All Content and Settings. Then Setup from an iCloud backup and you'll be set!