how do i connect my ipad 6 generation to external hard drive

Must use the official Apple lightning to USB3 CAMERA dongle which has a power through port in addition to the USB port.

You plug in the dongle to your device , then plug your lightning charger cable into the dongle and other end into the mains via the iPad charger plug (This provides power for the external drive ) and your USB cable between the dongle and your external drive preferably an SSD through you can get spinning discs to work in an external enclosure such as an ORICO - Which I am doing right now !

Caveat the lightning port makes transfer rates pretty slow in real world use especially when compared the newer USB-C ported iPadpro machines

The USB3 port also allows cabled mouses and keyboards to work

If you want to stick with SD cards for transfer just use the standard SD card reader dongle -these don’t require power and there are several third party versions of this

You would need an adapter for USB to Lightning. Also, if this external drive is one that has an actual spinning hard drive, it probably won't work. You need an external drive that is a flash style drive. The iPad does not have the power to get a normal physical drive to spin the way that it should and still be able to read/write to the drive.