Any Pentax K-mount lens will fit any Pentax DSLR. The DSLR will fire the shutter.  There is a menu setting (RTFM) which allows the use of older lenses, but you will lose some of the automation (again RTFM). Remember to allow that the effective focal length when using a "film" lens on a DSLR body goes up by 50%.
A standard 50mm lens becomes a 75mm equivalent, but stays a large aperture.

One problem the es 2 was a screw mount not a bayonet

No problems. Works like a charm. RTFM as already been said. Change a setting as indicated in TFM and you can use all your old Pentax lenses.
(Screw lenses with an adapter). Manual lenses in M-mode.
A-lenses in automode. Manual focusing with autoconfirmation for all lenses! Autofoccus lenses autocfocus of course.

Manual lenses= manual aperture and get automatic exposure time at the push of a button. Fully manual if you rather. Old K-mount lenses of different brands work brilliantly. Warning!! Some odd Ricoh with an exta pin in the K-mount may get stuck!!! Remove the pin if you have one. ( Only a few Ricoh K-mounted lenses!! )
All old m42-lenses work as well.
If I want to use something else than my umphteen
old Pentaxlenses, I put an old manual m42 lens by Carl Zeiss or a Rubicon 1000mm on my K100 or K10. AE and AF-confirm at will!
Quite a difference from Canikon.

In principle the Pentax bayonet has not changed. But it's the electronics which are not comparable between film and digital. The lense itself works, but it cannot deliver the information to the camera body for a shot. Your digital body will not fire since for it there's no lense attached.