It’s not surprising if you can’t see Find my iPhone Enable/ Disable option in iPhone settings app. Because it has been changed from iOS 10.2.1, iOS 11 and later updates. Now more options to manage iCloud account settings are under primary profile name at the top of the iOS settings app.
Find my iPhone and iPad is important and came in frequently use before restoring the device to iTunes or Clean iOS install.
Steps for Disable/ Enable Find My iPhone on iOS 10, iOS 10.2, iOS 11 or later
#1 Go to the Settings app on iPhone/ iPad
#2 Tap on Profile name, Next Tap on “iCloud”.
#3 Scroll down to screen, See option “Find My iPhone”. (Apple ID Password required)
Find My iPhone > Enable Toggle.
Location Service must be enabled to save current device location.
Remotely Check Find My iPhone/ iPad/ Mac is enable or not!
Find list of the device connected with same apple ID, See screen above.
Tap on it, to check it’s enabled “find my iPhone“, “Find My iPad”, “Find My Mac”.
Help: Sometimes I get a message “Trusted Device list is not available” instead of the list of devices. Close settings app from iPhone/ iPad and Recheck at the same place, hope it will available. I got it on my case now your turn.
Alternate options: Using Web manage all device. Go to icloud.com and Login with Apple ID and Password. Find account settings and manage devices for remotely erase or Call.
We recommended: Find my apple device must be enabled for all device to take advantage on lost or find from the misplaced area in office or home.
iOS 9 and Earlier iDevice: Find my iPhone/ iPad, Settings > iCloud > Find my iPhone and iPad.