If you update your current 7 server to 8 and then follow the steps mentioned here, you should be good to go. The reason I suggest updating to 8 first is that Server should upgrade the files on the Server into the 8.0 format as part of the upgrade process. Once this is done, follow these steps to change authentication methods:
Hope this helps. Also, please feel free to reach out to our support team if you need more clarification.
Thank you Dan, i'll try this steps and tell you about the result...