Can I load photos from a card reader or camera? On a iPad Air

See >>> Connect external devices or servers with Files on iPad - Apple Support

If you have fourth generation iPad Air, you can directly connect a camera or external card reader using the iPad’s USB-C port.

For earlier models of iPad Air, you’ll need a Lightning to USB 3 Camera Adapter:

https://store.apple.com/uk/xc/product/MK0W2ZM/A

There is no built-in SD Card slot/reader although you can purchase a "Lightning Port to SD Card Camera Reader" which may be of use:

Power & Cables - iPad Accessories - Apple