[Georgio]

Код:

@echo off

set n=5

for /f %%i in ('
 find /c "//=================="^<"example.txt"
') do (
 set /a n=%%i-%n%
 )
for /f "tokens=2 delims=:" %%i in ('
 findstr /n \/\/================== "example.txt"^| findstr /n "^"^| findstr "^%n%:"
') do (
 more +%%i<"example.txt">"new.txt"
 )

exit /b