What do i need to connect my new iPad Air 4th gen to my 10 year old iMac

You’ll need a USB Type-A to USB-C cable. Apple market good quality cables from Mophie:

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

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

mophie USB-A Cable with USB-C Connector (2 m)

https://store.apple.com/uk/xc/product/HN8A2ZM/A

You will need this USB-C to USB-A adapter

Tap the link below.

https://www.apple.com/shop/product/MJ1M2AM/A/usb-c-to-usb-adapter

OR an actual USB-C to USB-A cable.

You can find plenty of these on Amazon.

Best of Luck to You!

Much cheaper than this on Amazon.

Gimme a break!