We assume you mean a "bayonet" lens here.

Any lens you mount will be some form or bayonet, except for the "universal" 42m thread mount or the Canon FD breech mount.

An adaptor for an old manual Exacta MIGHT allow you to mount another lens, but expect no coupling to any of the mechanics of the camera and expect full manual operation.

Frankly, such an adaptor is a niche item that will cost you more than it's work.

p.s. My first slr was an Exacta Varex.

The old Exacta mount had a very narrow throat, the narrowest ever used, as far as I recollect. Therefore any "adapter" for any other lens mount will have to incorporate large-scale optical elements to try to bring the image from those lenses into focus in an Exacta. Thus it is very likely that the optical quality will not be good.

Basically, if you want to use the fairly plentiful supply of old "Pentax screw" (42mm screw) lenses, best to spend the money on buying a Pentax screw body.

yes