convert-ly seems not working

[Ledocq-Boccart]

Hi,

I'm managing converting  a *-midi.ly from 2.7.18  to 2.10.33
*-midi.ly is stored in "C:\...\Lilypond\usr\bin".
No answer found in the forums about the use of convert-ly
Environment: is Lilypond 2.10.33 running on win XP.
Formerly produced files *-midi.pdf,  *-midi.ps and  *-midi.log are erased.

_1. using convert-ly:_
typing    "C:\...\bin\convert-ly --from=2.7.18 --to=2.10.33 *-midi.ly"
produces (?)   *-midi.ly    which version remains 2.7.18 (reading
with jedit);
applying     lilypond.exe   gives:
*-midi.pdf            with unchanged scores
*-midi-log            no important error but again recommanding to use 
convert-ly  ...2.7.18 ... (2.7.38  2.10.33)


_2.questions:_
- Have I missed something?
- I wonder which syntax to be used fot specifying the --from and --to 
version:
--help shows 2 possibilities as in             " ... convert-ly 
--from=2.5.10 --to 2.10.33 foo.ly" example given

Thanks for answering!

Charlie