scanner to iPad

You don't.

iPads, even an iPad Pro, is NOT a full featured laptop computer.

There is no way to install device drivers and flatbed scanner software, in any iOS/iPadOS device, to operate an external flatbed scanner.

Currently, the only things that can be hooked up externally to an iPad are some wired mice, USB stick drives, external hard drives and SSDs, with caveats, and some USB hubs for use with some other low power peripheral devices, such as for use with certain audio production devices on iPads.

If you need to scan something, your only option is to use your iPad Pro's rear camera.

Sorry & Best of Luck to You!

Devices such a scanner or printer require installation of Device Drivers to add support for the individual device. iOS/iPadOS does not support installation of device drivers independently of an installable App. iOS/iPadOS instead use a driverless printing protocol known as AirPrint.

If the scanner that you wish to connect have a compatible installable companion App in the Apple App Store, then yes, they will work with your device - otherwise, no, connection with your iPad is not possible. Many AirPrint-enabled multi-function printers will have an appropriate App (downloadable from the Apple App Store) that provides the necessary driver-software.