The answer as usually is RTFM -> http://docs.jboss.org/jbpm/v5.3/userguide/ch.designer.html#d0e4435
But just in case that the documentation is not clear, you can try to migrate , but you need to understand that from jPDL to BPMN2 there is no one to one semantic mapping between the definitions, so I usually recommend to rethink your processes with the new semantic proposed by the standard. But this is just my personal opinion.
Cheers