Mike, Pavel is right about reading that link. ESSENTIAL
Perhaps also look at Development Environment
thread for Windows Development Debugging Environment - Setup Help
where Dave and Pavel helped setup a Windows compiling environment
. These are extensive notes about the process, and those notes & experience were used by Pavel to hone the thread he just gave you.
After you have cloned opencpn to your local repository successfully, you will need to create a build directory and run CMAKE from that directory (see the exact notes for this process in the link), then you will find opencpn.sln in the build directory.
However follow Pavel's thread carefully for the ENTIRE SETUP.... or nothing will work correctly.