Код:
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@Echo Off &Cls
Set "FileIn=Z:\Box_In\file.anc"
Set "BoxOut=Z:\Box_Out"
Set /A N=0, M=0
For /F "usebackq delims=" %%i In (`2^>nul More "%FileIn%"`) Do Call :Out "%FileIn%" "%%i"
Pause
Exit /B
:Out
If %2=="" If %N% EQU 0 (Set /A M+=1, N=1 &Exit /B) Else (Set /A N=0 &Exit /B)
If %N% EQU 1 2>nul Del "%BoxOut%\%~n1%M%%~x1"
Set /A N+=1
>>"%BoxOut%\%~n1%M%%~x1" Echo %~2
Exit /B
Вариант с лидирующими нулями в номере файла
Код:

@Echo Off &Cls
Set "FileIn=Z:\Box_In\file.anc"
Set "BoxOut=Z:\Box_Out"
Set /A N=0, M=1000
For /F "usebackq delims=" %%i In (`2^>nul More "%FileIn%"`) Do Call :Out "%FileIn%" "%%i"
Pause
Exit /B
:Out
If %2=="" If %N% EQU 0 (Set /A M+=1, N=1 &Exit /B) Else (Set /A N=0 &Exit /B)
If %N% EQU 1 2>nul Del "%BoxOut%\%~n1%M:~-3%%~x1"
Set /A N+=1
>>"%BoxOut%\%~n1%M:~-3%%~x1" Echo %~2
Exit /B