Using database with hyphen

db = db.getSiblingDB("dbname-w-hyphen")
db.dropUser("admin")

Get user

use db
db.getUser("root")

Get all users

db.getCollection('system.users').find({})

Create user who can readWriteAnyDatabase

db.createUser({ user: "<username>", pwd: "<password>", roles: [ { db: "admin", role: "readWriteAnyDatabase" }] })