How can I update Centos version to Centos7?

There are two options to upgrade centos on your server,
1. Re-format the existing machine and install CentOS 7, after you have taken a backup of the content.
2. Set up a new machine with CentOS 7, where you can re-upload your data and after everything has been configured, you would need to change the private nameservers that you are using and point them to the new set of IPs that will be assigned. We would be able to keep the old server up for one week while the content is being moved over.