How to sync the database with the microservices (and the new one)?

What if I'm going to create a new service? How do I get the registered user informations and put them in the new service?

You have to replay all events to which this new service is subscribed from the beginning of time (you should have an "event store" that keeps all events already happened in your application). Also, you can put a bit smarter logic when replaying events by starting from the most recent ones and going back in time. In this way, you will be able to restore most valuable data first. Just be careful to handle interdependent events correctly.

Data source: The events are pushed by the messaging queue(NSQ), If I'm going to copy the data from one of the microservices, how do I make sure the copy source has the latest user informations?

You are not talking about doing backups, right?

Aside from backups, in the event-driven systems people usually don't copy the data in a classical way, row by row. Instead, they just replaying events from event store from the beginning of time and feeding those events to the event handlers for the new service (or new instance). As a result, new service eventually becomes consistent with the other parts of the system.