how to rebuild the Eclipse project by importing the PAR, back-up or archive files?

Can you explain how to recover our eclipse project from the application server please? We do not have the original eclipse project created in NWDS on a local machine and so I need to figure out how to rebuild the project by importing the PAR, back-up or archive files. We are migrating from 7.0 to 7.4 and I need to import the eclipse project into net weaver developer studio and resolve some issues.