c++, search for a specific number in text file (notepad), move the number, and save it,

Question

hi everyone. I'm very new to C++. I installed dev c++, it works good coz I run simple program, and could receive the correct output.

Now I want to write a code to open the folder in my Desktop( How I can connect my code to this folder??). This folder including some text files (notepad). All of them has specific number in common, I want to read all this text file, find the number, and move the number to the other place ( 2 words back).
Finally save the edited textfile to the new directory.

Please help me, this assignment is due tomorow, and have no idea how to write it.

Thanks.