I can't guarantee that it will always be to the -3, but I can guarantee that it will be an "engineering" prefix that is some multiple of 3 (i.e. kilo, micro, pico, giga, etc.)
Format the cell(s) in question with the Custom format of ##0.0E+0 (this is one of the predefined Custom formats).
It wasn't my original idea; I think Jim Thompson showed me how to do it a few years ago.
Jim