how can I upgrade my ipad 3 with ios 5.1 to ios 5.1.1 and not to ios 6?

You cant...ios6 is the current update and nothing else is supported.

FYI

Here's what iOS 5.1.1 added http://support.apple.com/kb/DL1521

Just stay at iOS 5.1 until iOS 6.1 is released,

 Cheers, Tom 😉

The only way you could have done that would be to have done it before 6 came out. Like Tom says, just hang tight til 6.1 (that's what I'm doing)

Probably the next update will be 6.0.1.

Since the original poster doesn't say what his problems might be with iOS 6 it's hard to say much.