So ... mostly. The Mamiya lenses all have the same mount (except for the ones for the Polaroid SE, which you almost certainly don't have).
You probably have a Mamiya 'M' mount film back. This is long - wider than the camera body - and has rounded projections on each end where the film spools go. Most of the Press and Super 23 models have the M mount back that fits this. The body has two round knobs on the lower rear that turn to hold the back down. If you get a Universal, you have to make sure it comes with the "M frame" that fits the back. The M frame can be expensive to buy separately.
There are also less common Press and Super 23 bodies that have a rear "G" mount with sliders - this is the same as a 2x3 Graflok back, and works with a Graflok or RB67 film back. You probably don't want that.
The Mamiya Universal can take the M frame, a somewhat rare "G frame" that accepts the Graflok backs, or can take a Polaroid back that fits directly. If you see an ad for a Universal with a Polaroid back mounted, that means it doesn't have the M or G frame, which makes it less useful.