In many cases there are no equivalent header files. MS-Windows compilers do not normally support POSIX standartds or functions. However the MS-Windows port of GCC has ported many of the *nix POSIX functions to MinGW compiler.
If you want to find out what header file contains a specific function then google for "msdn function_name", replacing function_name with the name of the function you are interested in. Once you find the page on MSDN scroll down towards the bottom of the page and it will tell you the names of the required header files and library files.
This makes porting programs from *nix to MS-Windows difficult and time consuming.