https://www.amazon.com/Splitter-NEORTX-Enhancer-Adapter-Converter/dp/B07YTWTHHH/ref=sr_1_5?dchild=1&keywords=usb+micro+usb+cable+splitter&qid=1624235738&sr=8-5

Plug male micro usb into firestick. Plug power cord into female micro usb. Plug thumb drive into female usb port. Use ES File explorer to access the thumb drive.