In WF5 or earlier, Applications>Legacy (will be selected, you should select Standard instead)
In Creo, Options > Customize Screen, Commands Not In Ribbon, Legacy. Drag that into your ribbon or menu bar, then you can use it from there (here, it is a toggle).
Legacy was an old-school (Release 13, if I recall) application for direct manipulation of geometry. It was for the case where you had an imported part that isn't solid, and you wanted to make a change to it by hand (say, cutting a slot in the side). Very cumbersome, but it helped some customers transition from old CAD systems that didn't have feature-based modeling. Presuming this model is nothing of the sort, it had probably been put into Legacy mode when last worked on many years ago, so would retrieve by default that way.
