Format Number With Commas

I can't seem to figure out how to convert 10000 into 10,000 I thought the sh command might be it but either is wont support printf "%'d" or im doing something wrong... lol i hope im just doing something wrong

Just do $10000/1000$ or $mu(round, 10000/1000)$,$10000%1000$ if you want full control on the separator