Welcome to my life for the past few months trying to figure that out.
There is a large-scale data import and export function in Windchill to allow for large data migration, however it does not support migrations across releases (i.e. between a PDM 9 and PDM 10 system). This does kind of make sense given how many fundamental core changes can be made to the definitions of objects. There is a property buried somewhere either in the menus or on a property file on the server (sorry that I don't remember where) that will prevent an initial popup from flat out blocking you from doing a cross-release import by setting it to Yes to allow cross-release imports, however then the problem comes with data matching. There's the option of using a "mapping file" to help smooth over the import and unfortunately I don't have experience in writing those. But a good mapping file combined with that setting to allow cross-release imports should work.
Other option: Upgrade the older system first to match what you want to import the data into and then do the export-import. You still need to be careful right down to the last attribute. In the one I tried (i.e. bashed my face against a desk for a while trying to figure it out) not only were we trying to import data from an older Windchill iteration, they were in Italy. And a number of their data object attributes were in Italian. Which the import function couldn't find matches for in our own system. Which I usually only found out after an import attempt roughly one at a time since it throws the import after it finds a single problem.
....Want...to...crush...bricks....with...bare...fists...
I suggest the upgrade first then import later option.
Daryl
