How to see available RAM in iPad Air 5?

Apple does not expose the available RAM via iPad settings.

There are third-party utility Apps that can show the available RAM and local storage - along with other technical attributes of iPad and iPadOS. If interested in this information, perhaps consider System Status Pro: hw monitor:

https://apps.apple.com/app/system-status-pro-hw-monitor/id401457165

if you by ram mean system memory then you can't unless some thirdparty app from app store offer that option

if you by ram mean system storage then

How to check the storage on your iPhone and iPad - Apple Support