how do I generate a slide show of photos into Final cut as part of a presentation?

If you want to quickly and somewhat automatically produce a slideshow it may be easier to do it in iMovie, then import the resulting movie to FCP.

When you drag several images to the timeline in iMovie you have automatically applied "Ken Burns", whereas in FCP you need to adjust manually.

PNG is good, keep the quality. JPEG is fine, also. Just be sure the size the photos to your video frame size. Many times folks import HUGE photos (cause they're really big to start with) and it can bog things down unnecessarily.

Or purchase a slide show template from MotionVFX or the Coremelt VFX Market, or one of the many that sell them.