Working with archives in c++?

Question

C++ / C#

I have a string s, an integer n (> 0) and an archive file of integers containing data from several files in the format described in the task
As I understand it, I need to restore the file number n from the archive file and save it under the name s.
if the archive file contains data from less than n files, then leave the resulting file empty, but I don’t understand how to write it down