Syncing iPad pro12.9 fifth generation with iTunes on my computer

If you are attempting to use a “USB Adapter”, you may have difficulties - as these are a frequent source of issues.

Assuming that your PC (or Mac) has a USB Type-A connection, you simply require a suitable USB Type-A to USB-C cable. Here is one example marketed by Apple:

• mophie USB-A Cable with USB-C Connector (1 m)

https://store.apple.com/uk/xc/product/HN892ZM/A

If using a PC, it will require the latest version of iTunes. You may also use a Mac with iTunes or Finder - as appropriate for the installed version of MacOS.

Download and use iTunes for Windows – Apple Support

Update to the latest version of iTunes – Apple Support

Are you using a PC versus a Mac? Do you have Windows 10 and the latest version of iTunes? Did you get iTunes from the Windows store, or did you download it directly from Apple?