First, the floppy disk has a very small capacity - only 1.44 MB - you won't get much on a single disk.
When you want to copy, open the folder containing the files you want to copy, right-click and hold the right mouse button down. Drag the file to the A: drive icon in My Computer and release. A menu comes up offering Move, Copy or Create a Shortcut. Click Copy and the file will be copied.
Good luck - you will need a huge stack of floppies.
But first, why do you want to wipe your hard disk? There may be much better ways of achieving your desired objective.