If you want to draw in meters, you change the Units to Meters (type UNITS to open the Units dialogue box) and then you draw in meters. Or change it to centimeters. Or whatever you like.
One thing to keep in mind though, is that if you change UNITS, that doesn't affect what you have aldready drawn. You can't use Units to scale your objects from millimeters to meters. The Units-command controls how AutoCAD scales content (blocks and externals references) that you insert in your drawing.