Hi Ankitha,
You can look into this documentation on Hammerstein-Wiener Models, and on Polynomial Model Structure, and it may provide you some insight on how to begin.
If you can provide the code you've written to solve the problem and ask a specific question about where you're facing difficulty, we may be able to provide some further guidance.
If you aren't sure where to start because you're not familiar with how to write MATLAB code, I suggest you start with the MATLAB Onramp tutorial (https://www.mathworks.com/support/learn-with-matlab-tutorials.html) to quickly learn the essentials of MATLAB.
