What sort of project is your backup.cs
file in? Is it in a console application?
If so then you'll need to refactor your code so that the stuff that does the work has no user interaction or user interface (and yes a console is a user interface).
Once you have this code you can create a class library to house this code (so that it can be called from where ever you need it).
Then create a new Windows Forms Application and reference your class library. You can then hook up your UI elements (buttons etc.) to the methods in the class library.
To get a progress meter working you'll need call your procedure that does the work from a background worker thread. You may need to add events as well. These events can be subscribed to by the application to update the progress meter.