Now I change m2 and m3 to what on the clipboard. But that doesn't work when I have m2 and m3 in different colors and different fonts tru the lay-outs.
How can I find and replace m2 and m3 to m subscript 2 and m subscript 3?
Only m2 not 2 alone.
Your "Only m2 not 2 alone" seems to contradict what you wrote earlier, but I guess that what you want is to style 2 and 3 only when they are preceded by m. If that's the case, do this in the grep tab of the Find/Change dialog:
Find what: (?<=m)
Change to: <leave empty>
Change format: select subscript.
(?<=. . .) is a so-called lookbehind, [. . .] a character class. (?<=m) means 'preceded by' and  stands for '2 or 3'.
Thanks working perfect and also thanks for the extra info.