I use iOS 11.3 for iphone 6 plus , now icloud icon has been deleted from mobile setting any one can help me I use iOS 11.3 for iphone 6 plus , now icloud icon has been deleted from mobile setting any one can help me

This may not be what you mean, but the iCloud setting moved from older iOS versions. Currently, open the Settings app and then tap on your username near the top of Settings. The next screen then has iCloud settings.

Photos should be in the Photos app. Mail should be in the Mail app. Go to Settings/Your Name/iCloud, make sure you are signed in, and check to make sure Photos syncing is on. Then go to Settings/Accounts & Passwords to make sure your e-mail accounts are there and enabled.

The only files that will show in the Files app are data synced to iCloud Drive.

If the above isn't what you are asking about, are you asking about the iCloud Drive app? If so, that is now in the Files app.

Files app - Using