set /a Index=1

setlocal enabledelayedexpansion

for /r %%i in (*.jpg, *.png, *.webp) do ( 
    rem if number is less than 10, append 9 to file name
    if !Index! lss 10 (
        rename "%%i" 00"!Index!.*"
    ) else (
        rename "%%i" 0"!Index!.*"
    )
    
    set /a Index+=1
)