How to find quantization noise in my simulation? For college we have to make simple exercise in simulink (matlab). (since my professor is not familiar with simulink, he can't help).

The question itself is, how can I simulate the SNR when uniform quantization is used. To illustrate this: 

Because of this quantization there is noise. I need to display this noise. How do i do this?

Additional information: 10 bit quantization. The source has to be 40db.

I know i can get the quantization error when I subtract the output from the input but i do not know how to get the quantization noise.
The quantization error is the quantization noise. It is two different terms for the same thing.