It sounds like you're looking for content related to Direct3D Feature Level 12_0 or 12_1 (often referred to in older contexts as "Shader Model 6.0") and possibly a driver or DirectX runtime download. However, there is no official standalone “3D System Shader Model 6.0 download” — it's part of Windows and your GPU drivers.
Do NOT download from:
Update Graphics Drivers: This is the most common solution. The shader model is a feature of your GPU's driver. Visit the official sites for NVIDIA, AMD, or Intel to download the latest software for your card. 3d system shader model 60 download full
If you are a developer looking for the compiler to write SM 6.0 shaders, you should download the DirectX Shader Compiler (DXC) from the official Microsoft GitHub repository. Microsoft Dev Blogs To check your current version, run the DirectX Diagnostic Tool in your Windows search bar and looking under the tab for "Feature Levels" and "Driver Model". Are you trying to fix a specific error (like "Shader Model 5.0 required") or are you looking to develop software using SM 6.0? It sounds like you're looking for content related