@echo off
for /f "delims=" %%a in ('dir /b *.txt') do (
set "flag="
for /f "tokens=1* delims=:" %%b in ('findstr /n .* "%%a"') do (
if not defined flag (
echo.%%c>"%%a"&set "flag=a"
) else (
if %%b equ 8 (
echo %%~na>>"%%a"&echo.%%c>>"%%a"
) else (
echo.%%c>>"%%a"
)
)
)
)