Migrating OS X Server from Macbook Pro to Mac Mini
Tony, you might want to have a look at https://support.apple.com/en-us/HT202848

Migrating your Server
You can migrate from OS X Server on Mavericks or Mountain Lion to another &gt;computer using OS X Yosemite. Use the Setup Assistant or Migration Assistant &gt;included with Yosemite to transfer your data before you open Server app.
You can migrate server data using one of the following methods:
A server connected in Target Disk Mode
A local hard drive or partition with OS X Server installed
A local Time Machine backup of OS X Server
Migrating over a network connection, either from an existing server or a Time &gt;Machine backup, is not an available option for OS X Server.
To migrate your server:
Use Setup Assistant on a new Mac, or open the Migration Assistant from the &gt;Utilities folder.
Follow the onscreen instructions. Select a supported connection method when &gt;prompted.
When migration is complete, download and install Server from the Mac App Store
Open the Server app and follow the onscreen instructions to complete
the server setup.
If you open Server app before migrating your server data, remove Server app &gt;before migrating and then reinstall it after migration is done.