If you got a Micro-USB cable and adapted it to a HDMI cable, then connected it between your Raspberry Pi B+ and your Kindle Fire HD, would it work as a monitor?
Very unlikely. This is not simply a case of connector shape and size, but one of sending the proper signals and establishing the correct communications handshake. Not to mention a different number of wires.
However, you could use the Kindle Fire to access your Pi using XRDP as described here, this is a much simpler solution and allows remote access over wifi.