Lightening to usb which one?

Hello,

I recently purchased the new iPad 7th gen for use at my fire dept. so I will be using a flash drive 98% of the time. I purchased with my iPad the lightening to camera USB adapter to use my usb drive in. When I put my usb drive into the adapter and into my iPad my iPad pops a message stating this accessory requires too much power? My usb drive is 4GB, do I need a smaller one or what type of adapter do I need to purchase to be able to save files from my iPad’s Microsoft programs?

thank you!