Most space shipments are done with the standard cargo container. This universal sized module can hold several tons of cargo. Some quick deliverers take their trucks with goods loaded in the back and drive them right into the cargo container. They seal them up, deliver them to a new planet, and drive right out.
Most spacers know standard weights and volumes for common trade goods expected when picking up a container. Most ships with any hauling capability are suited to handle one or more cargo containers.