backup new ipad air to mac high sierra 10.13.6
I just got a new iPad air 5 and want to back it up on my old iMac (2011) running High Sierra 10.13.6. I've connected the iPad to my Mac using a USB C to USB 2 cable. iTunes (12.8.3.1) doesn't recognize the iPad and vice versa.
Mac System Preferences Network opened and says Thunderbird bridge not connected.
the iPad does not show in the sidebar of Finder where other devices are shown.
Is there a way to connect and backup my new iPad to my old iMac? Or will I have to wait until I replace my iMac sometime later this year?
iPad Air, iPadOS 15