How to add incrementing number prefix order by date on multiple files in Batch Script?

Here is a simple implementation of what aschipfl suggested in his comment:

@echo off
setlocal enableDelayedExpansion
set /a n=0
for /f "delims=" %%F in ('dir /b /od') do (
  set /a n+=1
  ren "%%F" "!n!_%%F"
)

But there are two potential problems:

1) The FOR /F command has a default EOL character of ; - if a file name were to start with ;, then it would be skipped. The simple solution is to set EOL to a character that cannot appear in a file name - : is a good choice.

2) The rename will fail if a filename contains a ! character because delayed expansion is enabled, and %%F is expanded before delayed expansion. The solution is to save the file name to a variable, and then toggle delayed expansion ON and OFF within the loop

@echo off
setlocal disableDelayedExpansion
set /a n=0
for /f "eol=: delims=" %%F in ('dir /b /od') do (
  set "file=%%F"
  set /a n+=1
  setlocal enableDelayedExpansion
  ren "!file!" "!n!_!file!"
  endlocal
)

There is a simpler option - use FINDSTR /N to prefix the DIR /B /OD output with the line number, and then use FOR /F to parse out the number and the file name. Now there is no need for a counter variable or delayed expansion.

@echo off
for /f "delims=: tokens=1*" %%A in ('dir /b /od ^| findstr /n "^"') do ren "%%B" "%%A_%%B"

You don't even need a batch file. You could use the following directly from the command line:

for /f "delims=: tokens=1*" %A in ('dir /b /od ^| findstr /n "^"') do ren "%B" "%A_%B"