Hi,
I am not sure I follow how this .dat fits into a Unity Project.
A PlayMaker template is a Unity Asset so you should have a file called "MyTemplate.asset". This is what you need to extract from your backup.
Also, Please make use of Github and sourcetree to maintain your backups for your project, it will really save you time and be a strong and flexible backup system for granular recovery.
Bye,
Jean