In order to migrate from On-Premises builder (brand) to Cloud brand you need to take the following steps:
Un-install current builder plugin from hosting panel(s). You can notify your clients about temporary builder disabling before plugin un-installation. The whole process can take up to 1 day (we migrate data only on business days!);
Create Cloud brand in Site.pro account;
Choose desired cloud builder server in Cloud brand and setup builder domain. Configure DNS settings for chosen builder domain so that it pointed to specified cloud builder server;
Archive folder data which is located in web root folder of On-Premises builder installation ("tar.gz" or "zip");
Contact us in the ticket and send us link to archived zip folder;
Wait for our response in the ticket when we restore archived data in chosen cloud builder server;
Install builder plugin on hosting panel(s) using installation guide link from Cloud brand.
We recommend you to create ticket before you start doing specified steps. It would be useful for us to know the size of "data" folder so that we better knew how much time data restoring can take.