Not working, missing delayed expansion support.

copy400.bat

@echo off

rem COUNT
set c=0

rem FOLDER ID
set f=0

mkdir folder%f%
echo Copiando a folder%f%...

for %%i in (*) do (
  if %%c LSS 400 (
    rem COPY TO CURRENT FOLDER
    copy %%i folder%f%\
    
    rem INCREASE ITERATION COUNT
    set /a c+=1
  ) else (
    rem INCREASE FOLDER ID
    set /a f+=1
   
    rem ADD A NEW FOLDER
    mkdir folder%f%
    echo Copiando a folder%f%...
    
    rem RESET ITERATION COUNT
    set c=0
  )
)