Which version of CUDA to install with GeForce 635M

I want to do some Convolution Network stuffs and make use of my old laptop with a GeForce 635M GPU. I tried to install CUDA 8.0 because this GPU has only a Compute Compatibility 2.1. When I run my script of the it shows it only use CPU:

The TensorFlow library wasn't compiled to use AVX instructions, but these are available on your machine and could speed up CPU computations.

I don’t know if my computer is really fit to do this.
OS: Windows 10

TF requires cudnn which requires a cc3.0 gpu. Your cc2.1 gpu is nearly useless with TF.