I always seem loose my SD to USB drive, so I made this mount that fits on the side of the ender 3 or almost any of crealitys ender series of fdm printers. Because of the metal frame, used it doesn't just have to mount to the top as shown in the image, but can be mounted to the side or any of the shown slots. ensure you download

'ender 3 usb holder (with mount)(v2).stl' if you want to attach to printer.