I have enabled Contact us form by Stores => Settings => Configuration => General => choose Contacts => Contact Us and set Enable Contact to 'Yes'.
But Contact Us Info block not display in Block section. What went wrong please suggest.
The standard way to confugure this if you have the sample data installed is to go into stores, configuration then general contact, enable contact. Then you will find the contact block and edit that. If you don't have the sample data then you need to make a new widget and associate that with a block.