Evaluating Steady State Error Constant for a Discrete Time Control System with Kronecker Delta Input

Hello there, hope you are doing well.

I am working on a Discrete Time Control Systems homework and at a certain part of it, the question asks me to find the steady state error of the system. I calculated the transfer function and found the discrete time representation of the system as well (checked in on MATLAB and everything seems correct).

However I did not find any information about how can I calculate the Steady State Error – Constant when the input is Kronecker Delta. I predict that I need to use Final Value Theorem and multiply the transfer function by something while taking the limit. I do not know what is that constant. Can you help me with that?