The second generation iPad Pro 11”, depending upon production date, will have originally shipped with iPadOS13.x - or perhaps for late production, iPadOS 14.x.
Assuming the iPad is new and unused, the iPadOS version installed from the factory is perhaps irrelevant.
During initial device setup, the iPad may automatically update to the most recent compatible production release of iPadOS. At time of writing, this is iPadOS 16.3.1.
If manual update is required, you’ll need to use either a Windows PC (with iTunes for Windows installed), or a Mac computer (with Finder or iTunes - 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
Update software on iPhone, iPad or iPod touch in iTunes on PC - Apple Support