If you were not using shared groups and your users had their contacts added manually, then i think every users has contact list stored in their profile. You can test this by temporary renaming Spark profile, forcing it to start a new profile and see if it fetches the contact list.
What i would do in your case (and i have just recently done similar thing), and this also applies to your other question about the name. But i had to assume you are using the embedded database and not the standalone MSSQL or MySQL or else.
Install Openfire 3.9.3 on another server, but do not run.
Stop old server and copy embedded-db folder, conf folder to a new server
Then rename new server to the same name as it was on a Windows box (hostname)
Run the new Openfire.
You say that you need only contacts, but without the actual users the contacts are useless. Doing it the way i described is easier than exporting importing, especially when there is no version of that plugin for such an old Openfire version.