You are using Compact Edition which is still supported but by default SambaPOS no longer uses it. The default setup is LocalDB which is SQL Server Express. If your upgrading your system I recommend migrating it to SQL Server 2014.
You can get detailed instructions on setup and how to migrate the CE database over to it here:
Once you get it switched over to SQL Express backup and restore is very simple and can be done from within SambaPOS if you purchase the module. Can also be done with Microsoft SQL Server Management Studio.
SQL Server offers more advanced functions of SambaPOS4 that CE can not offer.