@echo off&setlocal EnableDelayedExpansion

set a=1

for /f "delims=" %%i in ('dir /b *.mp4') do (

if not "%%~ni"=="%~n0" (

if !a! LSS 10 (ren "%%i" "b0!a!.mp4") else ren "%%i" "b!a!.mp4"

set/a a+=1

)

)