Ok i have been using autocad 2012 for some time now so i end up getting ahead of my teacher, well i created 2 drawings according to the book we are using, but he decided he wanted the drawings done in MM instead of Inchs, so i was wondering if there is a way to covert my drawing from inch to MM?
If the units drawn represent inches you can use the SCALE command and scale up all your objects by 25.4 to make them represent millimeters.
You could use the SCALE command to change the size of everything, but in the real world thats like hitting it with a sledgehammer. You will end up with odd-numbered sizes which is usually discouraged; most things need to be built and those in the field work faster with 1000mm instead of 1016mm. Certain manufactured objects are constructed and/or labelled differently in metric units than they are in imperial units so may not even be available in the that converted size.
Are you to change the physical size or only the units of the dimensions? If you only need to convert the inch dimensions to equivalent size metric dimensions - that is pretty easy to do in the dimension styles.
...or you start a new drawing with a metric template, copy and paste the imperial one into the metric one, find a known metric dimension, then scale the whole thing by reference to the new dimension...