Already answered this by e-mail, but for the benefit of anyone else reading:
It's not as easy as it should be, unfortunately; basically you have to export the flashcards to a text file, copy that text file over to your Pocket PC, and then reimport them on your Pocket PC. To do that, go to the Manage Flashcards screen on your Palm and use the Export command to save all of your flashcard lists to a text file, in UTF-8 encoding, on an SD card. Then, put that card in your Pocket PC and use File Explorer to copy the text file into your Pocket PC's My Documents folder. Finally, go to Manage Flashcards on your Pocket PC, and use the Import command to import that text file back into PlecoDict.
There's no way to preserve your flashcard statistics, but this would at least keep the vocabulary intact. If you can wait a few months for the finished release of 2.0, the utility we're releasing to convert flashcards from Pleco 1.0 to Pleco 2.0 format actually will leave statistics intact, and files from that can easily be moved between platforms.