The MaestroEasyExampleCpp example in the Pololu USB SDK has references to the precompiled versions of UsbWrapper.dll and Usc.dll that come with the SDK. You can see the references by looking in the .vcproj file with a text editor. Those references should allow the compiler to find those DLLs, which are in the folders UsbWrapper_Windows and Usc/precompiled_obj.
If you are using Visual Studio, it’s possible that it did a bad job of converting our project files to the latest format, and it might have deleted those references. You might try adding those references to your project the same way you would add a reference to any other precompiled .NET DLL. Microsoft has an article about that here: