Most (all?) iPad Air models have a Lightning socket.
You’ll probably want and need a USB-A to Lightning cable here, minimally.
Apple has one- and two-meter variants.
https://www.apple.com/shop/product/MXLY2AM/A/lightning-to-usb-cable-1-m
Before you invest in the Lightning cable, check the USB outlet power output specifications for your vehicle.
That’ll often be in the vehicle owner’s manual. If not, check with the vehicle dealer.
I’d expect many vehicle USB-A outlets to supply 5W, and that’s insufficient power for charging an iPad.
Some vehicle USB-A outlets might offer 10W or 12W, and that’ll be marginal to acceptable for charging many iPad models. Slowly.
Apple wall-warts intended for iPad charging have been 10W and 12W for a long while (older USB-A), and variously higher (USB-C). Not 5W.
About Apple USB power adapters - Apple Support