Either draw in meters or in millimeters, like ReMark said, we (and your teacher) can't know what is what. I at least have no idea what the objects that you have drawn are so I can't recommend if meters or millimeters is the best.
I have drawn most of my career in millimeters and just recently switched (along with the entire office, hilarity ensued) over to meters so I know your pains with the scaling in the viewports.
I gave an example previously about what scale you should have on your viewports if you draw in meters in Model Space. Here's how to calculate that on your own: If you want the scale to be 1:10 when all is done, then the scale you set on the viewport is 1000 x (1/10) = 1000/10 = 100/1. You multiply it always by 1000 to overcome the difference between model space (meters) and paper space (millimeters). So the scale 1:200 becomes 1000 x (1/200) = 1000/200 = 1/0.2 .
If you draw in millimeters in Model Space, the last paragraph doesn't apply, just set your scale on the viewport to the correct scale.