When trying to do transfer functions in matlab one very nice way to do it is with
s = tf('s');
Now, s indicates it is a transfer function you can actually just type the rest of your equations as you would want.
k = k; d = d; tau = tau; % These are just saying that you should define these yourself
G = k*exp(-d*s)/(tau*s+1); % Create the transfer function
step(G); % Plot the transfer function
