Holy cow, after the latest updates I can confirm those DX9 files are no longer in the Windows\System32 folder in both Win 10 builds 1511 and 1607 (I don't know about 1703 as I no longer have anything running that) as well as Windows 7. Looks like Microsoft decided to "fix" the problem they created two years ago by hiding the files too, making any workaround more difficult.
However all of my DX9 games still work fine, including the non-Steam version of San Andreas
so the files are still somewhere. Games that required a .dll in the game folder still stop working when the file is removed, so games continue to look in the game folder first, it's just trickier to get the files.
There are a lot more DX9 files than your pic shows, but I don't know which GTA:SA uses so you may want to try extracting that DirectX 9.0c installer and putting all the .dlls into the game folder (if there's only .cab files in there then you have to extract the .dlls out of the .cab files).
Or in the GTA forums, someone said:
In your GTA:SA folder d3d9.dll is the DirectX 9 file required, however, GTA:SA doesn't detect it. To fix this problem, rename it to d3d9_32.dll