If a game gives you an error saying a .dll file is missing (like d3dx9_43.dll or d3dx11_43.dll ), it is asking for DirectX 12. It is asking for legacy DirectX files that are not included in a standard Windows 10 installation.
How to install the latest version of DirectX - Microsoft Support directx 12 windows 10 64 bit offline installer
DirectX 12 offers several key features that make it an attractive choice for game developers and Windows users: If a game gives you an error saying a
You will notice the keyword "64-bit" in our focus. Windows 10 is predominantly a 64-bit operating system. A 64-bit version of DirectX 12 allows: Windows 10 is predominantly a 64-bit operating system
Click → choose dxwebsetup.exe (approx 300 KB).
: Fully offline; fixes missing .dll errors (like d3dx9_43.dll ) for older games.
If you are looking for an offline installer because you are having trouble with a game or application, here is how the "installation" actually works on Windows 10 64-bit: How To Download & Install DirectX 12 (Windows 10 & 11)