trying to find my iPhone after plugging it to desk top Mac its not in the side bar in FINDER

Open Finder and click on Settings in the Finder menu. Then tap on Sidebar and make sure all boxes are checked.

In the Finder window itself click on “>” to the right of Locations if it isn’t listed your connected devices.

Standard stuff. Shut down the Mac. Restart the iPhone. Connect the phone with a cable that you know is working.

If you have not done this in some time, you may see a notification on your Mac asking you if you want to Trust the iPhone. Click Yes.

Then tap Settings on the iPhone and look for a similar notice asking you if you want to Trust the Mac. Tap Trust.