If you find a workspace file (.jws) just go to File -> Open -> Application and open it.
If there is not a .jws file, then
you should look for a project file (.jpr). So you should create an application first and then go to File -> Open -> Project and open it.
You should upgrade to JDeveloper 11g that is really better than 9g, unless this project is tightly related with a 9g technology.
The most appropriate place to get good answers is
JDeveloper 11g Technology Preview Forum.
Thanks.