I do not know that, but i know that if you create a Ukash account you can go to Toolkit and convert your German ukash to any other available currency
That is unfortunately no longer the case:
Ukash codes issued in Germany cannot be converted to another currency using Ukash Tools. We are sorry for any inconvenience caused by this change.
Ukash codes issued in Germany cannot be combined, split or converted to another currency using Ukash Tools. This change is made due to changes in German financial regulations. We are sorry for any inconvenience caused by this change.