"Cargo" is the generic term for anything being transported. It is often stored in a cargo bay and/or in cargo pods.
Cargo can refer to more than simply inorganic matter, however. Anything being transported is considered cargo and that can include sentient lifeforms. In 2368, an empathic metamorph named Kamala was cargo to the USS Enterprise-D before being disturbed from her cocoon early and then empathically bonding with Captain Picard. (TNG: "The Perfect Mate")