how to turn find my icloud off

See Set up Find My iPhone https://support.apple.com/en-us/HT205362

You need to have turned on Find My iPhone from this point on. See the steps in the first link below especially, but don't ignore the second.

If your iPhone, iPad, or iPod touch is lost or stolen  https://support.apple.com/en-us/HT201472

Use Lost Mode in Find My iPhone on iCloud.com https://support.apple.com/guide/icloud/use-lost-mode-mmfc0f0165/icloud

If you have access to the phone, go to Settings/Your Name/iCloud, and you can turn it off. If you lose the phone, you won't be able to track it.