Deleting files from usb on the ipad

Hi guys,

I’ve uploaded some files from the iPad Pro onto my usb stick. I want to edit and delete some of the files from the usb stick (isn’t the same iPad) and although it appears to let me delete some of the files, when come off and go back in, those deleted files have reappeared(?) So I guess the question is how can I make permanent changes to the files on my usb stick?