Question
my orchid stem is going black what should i do and how do i find out what type it is?

Answer
Kelly, the most commonly found pot orchid at commercial retail outlets is the phalaenopsis (aka Moth) orchid.  These have usually 3-5 oval leaves and, when in flower, have a flower spike (ie stem), originating at the base of the plant, from which floral branches occur.  These usually bloom in the spring and may remain in bloom for a month or more.  When flowering is done, the flower spike may die back and may be cut off.  These plants should be repotted in a special orchid potting mix after each flowering using a plastic pot with lots of drainage holes.  You may google "phalaenopsis" or "moth orchid" to find pictures to confirm whether your plant (or my description) fits.