Код:

@Echo Off
cls
Set /A N=0
Call :NFiles "Z:\Box_In\*.txt" "N" "M1"
Call :NFiles "Z:\Box_In\*.bat" "N" "M2"
Call :NFiles "Z:\Box_In\*.zip" "N" "M3"
Call :NFiles "Z:\Box_In\*.js" "N" "M4"
Echo %N%
Pause
Exit /B
:NFiles
SetLocal
Set /A N=0
FOR /F "usebackq tokens=*" %%a IN (`2^>nul Dir %1 /B /A:-D`) DO Call Set /A N+=1
Echo %1 - %N%
EndLocal &(Set /A %~2+=%N%) &(Set %~3=%1 - %N%)
Exit /B