With the release of 3DF 30.40, project files are no longer included in the customer packages. The package includes CMake files which can be used to generate the build/project files you need. CMake is an open-source, cross-platform tool. You will need to download / install CMake - Upgrade Your Software Build System (at least v3.31).
After downloading the 3DF package, you can generate build/project files using a cmake command like the following;
cmake -S . -B ./build -G "Visual Studio 16 2019" -DCMAKE_BUILD_TYPE=Release
Basically, this command generates Visual Studio 2019 project files in a directory called build.
For more detail including usage on other platforms, please review the README.md included at the root level of the 3DF package.