Rc12 is a remote model number, what we need is the name and model number of roku itself. Is it a purple stick? If its the 3500, keep a hold of the remote because there is no replacement for it, ever. All sticks pretty much use micro-usb cable, accept for stick+ that uses a mini-usb cable.
https://www.roku.com/products/accessories/streaming-stick
first one listed above should work, PW03.
Edmund