what atf oil do I put in? on 2001 BMW Z3

I have a 2001 z3 with a 5-speed manual tranny and a 3.0 efi engine,my ? is I have a filler unit next to the oil filter which states ATF oil only,and I need to add some,what kind of ATF can I use?

Asked by for the 2001 BMW Z3
the round object next to your oil filter is the power steering reservoir and has nothing whatsoever to do with the transmission. it uses plain old Dexron III red transmission fluid and does not use power steering fluid.
the transmission does not have any filler or dipstick; it is filled at the top of the transmission and uses a special
BMW only fluid.
Thanks for your help,I was a little confused there when the cap said use ATF only.