Sql-server – Setting up SQL Server 2008 R2

installationsql-server-2008sql-server-2008-r2

I need to set up a SQL Server for a development environment for a client. First I installed SQL Server 2008, I was able to connect to it from SQL Server Management Studio fine but when I tried to restore the .bak it said

the database was backed up on a server running version 10.50.2789.
That version is incompatible with this server, which is running
version 10.00.5500.

After googleing I found I needed SQL Server 2008 R2 to match that version number, so I downloaded that from the Microsoft website and ran it. But I keep trying to set up a new server instance so I can restore the .bak but it's still creating another instance in SQL Server 2008 when I install it with version number 10.0.1600.

Can anyone suggest how I can set up a server running version 10.50.2789?

Thanks