Connecting Washing Machine Outlet Box to copper
If you look closely at the valve inlets, they are designed with a 1/2" male iron pipe thread (MPT) for a threaded connection, OR you can solder 1/2" copper pipe directly to the inside of the threaded fitting. It's made to accomodate either method.

You do not need any additional fittings.

You need to be careful though, there are o-rings and teflon seals inside the valve that can be damaged by the heat from soldering. You need to take it apart by removing the large screws next to the handle, solder the included fittings, then reassemble.

See this schematic.