Once your Vectorworks is converted into a license without dongle (serial number starting with “E”), you no longer need your dongle. Make sure to send all the dongles back to Design Express Netherland, Belgium (NL/FR) or France.
If you are not sure how many dongles you have, remember that each dongle corresponds to one Vectorworks license. You can find the exact number of licenses on the Vectorworks Customer Portal (if you are a Vectorworks Service Select member) or on the registration card you received from Design Express.