@echo off

Setlocal Enabledelayedexpansion

(
  echo;854/FLammrock
  echo;12/LOL
  echo;259/Salut
  echo;7458/Test
  echo;125/Oui
  echo;36/NANII
)> myFile.txt

call :sort myFile.txt


pause&exit
:sort <File>
  type nul > "%temp%\tempfile"
  for /f "tokens=1,2 delims=/" %%a in ('type "%~1"') do (
    set /a seq=1000000000+%%~a
    echo;!seq!/%%b
  )>>"%temp%\tempfile"
  type nul > "%~1"
  for /f "tokens=1,2 delims=/" %%a in ('sort "%temp%\tempfile"') do (
    set /a seq=%%~a-1000000000
    echo;!seq!/%%b
  )>>"%~1"
goto :eof