Remove a device in Find My on Mac
If you’re no longer using an Apple device, you can remove it from Find My. If you’re planning to give it away or sell it, you should erase it first.
Note: See the Apple Support articles for full details about preparing to sell, give away, or trade in your Mac, iPhone, iPad, iPod touch, or Apple Watch.
In the Find My app
on your Mac, click Devices.In the Devices list, select the device you want to remove.
Click the Info button
on the map, then click Remove This Device.Note: You can also Control-click the device in the Devices list, then choose Remove this Device.
When you remove a device from Find My, Activation Lock is turned off immediately.
You can also remove the Mac you’re using—choose Apple menu 
Click Overview in the sidebar, then click Sign Out.
Signing out of iCloud turns off all iCloud features on the device. See If you sign out of your Apple ID preferences.
Click iCloud in the sidebar, then deselect Find My Mac to remove your Mac.
For information about using Find My with other devices, see the user guide for iPhone, iPad, iPod touch, or Apple Watch, or the AirPods Support website.
Note: If you no longer have a device (Mac, iPhone, iPad, iPod touch, or Apple Watch), you need to remotely erase it before you can remove it. See Remotely erase a device.