To download pixel shader 3.0 can any where you can find it ...

Shader Model 3.0 support can be implemented either in software or hardware. In the case of a software implementation, you can download it. One example of a software graphics implementation that supports Shader Model 3.0 level capabilities is SwiftShader.

For hardware support, which is generally faster, you can't download it. It's a feature of the hardware itself so you'll need to upgrade your graphics card if you current one doesn't support it.