This article explains how to connect an iPad to a USB device. Instructions apply to all versions of the iPad.
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The following iPads have a USB-C port:
These models allow you to connect any USB-C device that is compatible with the iPad. With these models, the problem of connecting USB devices to the iPad is solved, assuming you connect USB-C accessories. If you have an older USB device that you want to use with these models, you will need an adapter. You can purchase a USB-C to USB adapter from Apple . Connect your old USB devices to this adapter, then plug the adapter into the USB-C port on the iPad, and you are good to go.
If you have an entry-level iPad, an iPad Air released before the 4th generation, an iPad Pro released before late 2018, or an iPad mini released before the 6th generation, you'll need an Apple Lightning to USB Camera Adapter to use USB devices. You plug the adapter cable into the Lightning port on the bottom of your iPad and then connect a USB accessory to the other end of the cable.