Each Cloud server has its own DNS servers, so in a generic guide like this one, we can't tell you which DNS servers to use but yes how to get them.
Method 1: Check the Welcome email
When we initially activate the server, we send a welcome email with the correct DNS servers for your Cloud Server. Just check that email message.
If you do not find the welcome message, please contact us as soon as possible.
Method 2: Verify the DNS Servers in your Cloud Panel
You can find your DNS servers in your Cloud Panel, under the list of created hosting accounts.