Those should be Power Gear jacks, and they retract solely by spring tension. However, there may also be a grease fitting near the bottom end of the jack cylinder. If there is, give it a few squirts with a grease gun. Sometimes the seal gets dry and the jack won't quite slide up all the way. Lubing it helps.
They are a widely used jack system and parts should be available through most any RV dealer. Does not have to be a Southwind or Fleetwood dealer.
Buy Replacement Parts - Power Gear