I have an iMac i5 2017 with a good display. Can I connect it to 2024 mac mini and use my iMac s display?

That setup is not supported by Apple. The old iMac cannot be used as a monitor for any of the newest Macs and Target Display mode is no longer a feature of macOS, having been deprecated years ago.

Please see: Use your iMac as a display with target display mode - Apple Support

Per the link above:

• Your target iMac (monitor) must be using macOS High Sierra 10.13.6 or earlier. 

• In all cases the source Mac that you're connecting FROM must have been introduced in 2019 or earlier and have macOS 10.15 Catalina or earlier installed.

You might consider a third-party solution - Luna Display or Duet Display - though I can’t speak for the performance of those. Regardless, you still will need a proper monitor to set up either of those options.

Do yourself a favor, avoid the headache and just budget an extra $100 for a monitor. Yes, they are that inexpensive.

Be aware that the third-party solutions the to turn an iMac computer into a monitor are laggy, and unsuitable for a primary display. They would be fine for parking static items like palettes and Finder windows to make room on a main monitor, but not as the ONLY display.

This disclaimer, on the main support page for Luna Display, speaks volumes:

The red emphasis is theirs, not mine.

Save yourself a lot of grief and get a proper free-standing monitor. It will provide full motion video, better display options, fast response, and use less power.

Not with Target Display Mode. Apple discontinued that in Late 2014 when the first 27" 5K Retina iMac came out. Your 2017 iMac is too new to have it. On top of that, current Macs don't support using any Mac (even one which does support Target Display Mode) as a Target Display.