Once you have the new DFM server installed, you can backup your existing DB and restore it to the new DFM instance....
This is a snip from the Operations Manager Administration Guide...it's available from the NOW site for downloads.
Restoring the database from the archive-based backup
You can restore the DataFabric Manager database on the same system. You could specify the absolute
path for the backup
file using the dfm backup restore command.
Copy the backup file into the databaseBackupDir directory.
Type the following command at the command line: dfm backup restore <backup_name>
backup_name is the name of the
file to which you saved your DataFabric Manager database.
“Completed restore” message is displayed when the restore process finishes successfully