I want results plot of PSD in (m/s2)2/Hz

    % code
 % Firstly, I generated a random road profile in Matlab using this code.
   t=0:0.0121:10;
x=zeros(size(t));
z=zeros(2500,length(t));
freq=linspace(0.02*pi,6*pi,2500);
b0=7.8*10^(-8)*((freq).^(-2.1));
a0=sqrt(b0);
p=2*pi*rand(1,2500);
for n=1:2500
    x=a0(n).*sin((n*0.628*t)-p(n));
   z(n,:)=x; 
end
tt=zeros(length(t),2);
tt(:,2)=sum(z);
tt(:,1)=t;
o1=0.1:0.01:3;
p1=4.5e-6*(o1.^(-2.1));
[pp ww]=pwelch(tt(:,2),45,43,[],(1/0.0121));
loglog((ww/(12.5)),(pp*(12.5)),'r',o1,p1,'g')
  end

 % secondly, I got this plot:

   % Next, I run my vehicle model in Simulink and I got graph in scope which is given "to workspace" block.
   % Finally, I run Pwelch command in which i gave this scope result as input signal, I got this graph of PSD:

   % I want this Y-Axis in (m/s2)2/Hz

could you please help me what to do next??