Hi I'm looking for man pages package for C++ commands, so when I type:
"man fstream" or even something simple like "man cout"
I would get the man pages and not an error of: "manual entry does not exist" or something like that.

I already have installed manpages and manpages-dev, but they only gave man pages for C commands not C++ commands.
I also installed manpages-posix and manpages-posix-dev, but removed them after I saw that they don't give manpages for C++ commands.

So which package do I need to install to get manpages for C++ commands?

There is some html based documentation in the libstdc++<version>-devel packages.

For example, on my computer:
file:/usr/share/doc/libstdc++6-devel-3.4.1/html/index.html

Otherwise, perhaps the source of this package could be rebuilt to provide man or info pages.
But I haven't checked.

Please look at ftp://gcc.gnu.org/pub/gcc/libstdc++/doxygen/