changing the scale

I scanned a printed drawing and imported it into autoCAD and my question is how do I change the scale of the drawing to what I need it to be, which is 1:500. Many thanks.

edit: I think I worded my question wrong, in the file that I scanned in the scale is all wrong, actually it isn't scaled at all. So actually my question is how do I make a scale. eg. my one wall measures 3 meters in my scanned image but actually I need it to measure 47 meters.

Hopefully that make it more clear, thanks very much.

use the Reference option in scale. In this case select your image, select a base point, type R then 3 (old length) & 47 (new length)

Oh ok, thank you very much Dave.