I have been working with Auto CAD for quite some while now and I still get stuck on this problem. I get given a loft of drawing that were done in 3 party software so when I receive a drawing that I need to work on I always start off with the what the current scale a the drawing is.(sometimes the drawing gets done in meters in the 3 party software and when I pull it into Auto CAD it interprets the meters as millimetres which means I basically have to scale the current object with a 1000 so that it would be the correct size. I have always done this by checking the scale of the objects in the current drawing. I have attached a dwg. where I adjusted the units three times (Millimetre ,Meter and Kilometre) but when I draw A line of 1000 units long ,in  all three unit types the line is the same length .Common sense tells me that the line drawn in meters would be longer than the line drawn in millimetres ,same when it comes to the length difference between the one drawn in meters and the one line in kilometres.

So basically when I open a dwg. how would one know the current size (when measuring ) of an object  as well as how would I change my drawing units so when I measure an object the current dimension displays either millimetres ,meters or whatever I would like the units to be.

Can you please assist me with this problem?

Henry Klopper