how to find values which are greater than 1000 in indesign, because every time I have change the thousand separator throughout the file
I haven't a clue what you're asking for. You'll have to provide more information.
Start with what version of InDesign (exact version) you're using, what operating system. Give a complete description of exactly what you're trying to do.
How about a GREP Find/Change? This will get you started:
Retrieving data ...