SanDisk USB C connection to. iPad Air 3?

Hi,

I have an iPad Air 3 and want to connect a SSD SanDisk with a USB C connection to the lightning doc on the iPad. Currently I have the 1 TB drive connected to a Apple Lightning Camera Dock with a USB C to USB cable and have the Apple Dock connected to my iPad’s lightning connection. I have the Apple Camera Dock with the additional Power Port plugged in. However I keep getting the message that there is not enough power to connect this device?

What is wrong with my set up?

Thanks,

David