MongoDB not creating database in shell

It will not show until your database is empty. To have your database shown you can use

create collection command to insert collection then it will be shown to you by using

show dbs

Per the MongoDB documentation:

If a database does not exist, MongoDB creates the database when you first store data for that database. As such, you can switch to a non-existent database and perform the following operation in the mongo shell:

use myNewDB
db.myNewCollection1.insertOne( { x: 1 } )

The insertOne() operation creates both the database myNewDB and the collection myNewCollection1 if they do not already exist.