USB of the New iPad

USB-C is a physical/electrical interface specification - not a guarantee of capability. A device equipped with a USB-C port does not necessarily support all USB or USB-C device types or hardware - support for any device is determined by the device-driver software that may (or may not) be installed upon the device.

The 2018 iPad Pro, like iPad every before it, has very limited support for external devices.

Now to you question, if you can provide us with a little more information about "what" you are trying to do, we may be able to assist you with advice about what is supported - and/or how to achieve your aims.

USB thumb drives are often problematic when connecting to an iPad. Many of these devices require more power than the iPad can directly provide - often necessitating connection via an intermediate self-powered USB hub.

You should also be aware of limitations associated with iOS and USB storage. Support for file types are highly limited; many file systems (such as NTFS) are not supported; file and folder structure and naming must typically conform to the structure typically found on a digitial camera card. The USB device cannot be formatted to a compatible file system by iOS; formatting to a compatible file system must be performed externally using a PC or Mac.

Other proprietary USB devices exist, together with an associated device App, to facilitate file transfer between the iOS and storage devices, however, support for file types generally remains limited to those natively supported by iOS.

I hope you find this to be of some help.