Can I use a SD card reader with my iPad Air?

Yes. Your iPad can be used with an SD Card Reader. You can either use a dedicated USB-C to SD Card Reader, or use one of the many compatible USB-C hubs that incorporate an SD Card Reader.

Apple market their own Adapter:

USB-C to SD Card Reader

https://store.apple.com/uk/xc/product/MUFG2ZM/A

Additional information about connecting external storage to your iPad can be found within the iPad User Guide. Here is a direct link to the relevant section of the Guide:

Connect external storage devices to iPad - Apple Support

You’re very welcome.

Here’s another link - this time for a USB-C hub that incorporates SD and microSD Card readers, HDMI, USB Type-A ports and USB-C that also support USB PD (Power Delivery) pass-through - to which you can connect your iPad Power Adapter or PowerBank.

Kingston Nucleum

https://www.kingston.com/unitedkingdom/en/memory-card-readers/nucleum-usb-type-c-hub

USB-C hubs are more versatile than a simple SD Card Adapter, permitting simultaneous connection of multiple devices. Perhaps consider Kingston, Anker, Hyperdrive and Satechi - although there are many others from which to choose. A Google Search for USB-C Hubs compatible with iPad will find a number of articles and recommendations.