For adding "something" behind the numbers just use adding in string mode as said @MJV.
Here is simple example with existing/known number line. Using this way no matter if your numbers are integers/reals with few decimal places, "m" will be always added at the end of number. If you need one empty place before m (offset m by one empty place), simply change constant string value to " m" (empty place, then m)
add_string_mode_scene.c4d