How to identify parameters of the model?

I have a black-box model in simulink with 2 inputs and 1 output.

I also have a nonlinear equation describing the same model, which I have put to simulink. However, this equation has unknown parameters (5 unknown gains).

How can I find the values of these gains such that the response of the system I made in simulink would be the same as the response from the black-box model?

Thanks.