How to connect apple tv 3rd gen to imac itunes to restore

Here’s the link to the support article about it: Restore your Apple TV - Apple Support.

It lists the procedure in 8 steps.

What macOS version is your iMac running?

If its running macOS 10.15 Catalina or later, the Apple TV should appear in the Finder under locations. You plug in the Micro USB cable to the Mac and then connect the Apple TV to power.