Hello,

Yes, indeed you are correct. What you need to do is:

• Make sure that your wp-config.php files for your new subdomain names are set to the new databases and database users that you’ve created

• You need to run a search and replace for your new databases to update all of the references for your domain to your subdomain name

For example to do that you could either use the wp-cli toolor the following script:

https://interconnectit.com/products/search-and-replace-for-wordpress-databases/

If you decide to go with the wp-cli tool, the command that you would need to use would look something like this:

wp search-replace 'http://example.com' 'http://sub1.example.com'

It is best to run that command from within the document root directory of your new sub domain so that the tool could pick up the database details from your wp-config file.

Note that this is a really dangerous operation as it can mess up your whole database in case anything goes wrong so it is very important to always make a backup of your database before proceeding with the operation.

Hope that this helps!
Regards,
Bobby