Okay, the drain plug for your boat, should be the lowest drain/opening on the back of the boat. It should have a plug (either all the way screwed in, or 'hanging out' with a safety connection). It is threaded, and accepts a male 'stopper'.
The drain (on the inside of the boat) is always in the lowest possible position in the inside transom area, to allow for complete draining of the inside hull area.
On some boats, there is a higher drain that allows 'overwash' that comes over the transom area to drain out - just in front of the engine. It generally has no 'plug' and also no threads in it.
If you are a first time boat owner; and especially if this was a new boat; the dealer should have gone over all of this with you. Likely should have taken you on a 'maiden voyage' also.
Don't worry about asking seemingly 'stupid or first time questions here' - we all have. And some of us continue to do it. Enjoy your boat and welcome to the site.
Tex