After restoring my iPhone I'm unable to Sign-in to iCloud account

What do you mean when you say you lost you iCloud? iCloud is not a tangible thing, it is an electronic service.

Are you signed in and iCloud activated?

This document tells you how to sign into iCloud --> Set up iCloud on all your devices --> Sign in to iCloud on all your devices - Apple Support

Change your iCloud feature settings [iOS and Mac] - Change which apps sync and store data with iCloud - Apple Support -