How to plot a 3D function?

I'm trying solve this problem for the last one year but unable to do so. Please if anyone can help me.

I roughly code a program but don't know how can I plot it.

N0=100;
r_med=[0.445 0.889 1.445 2];
sigma_g=7;
N_ang=91;
theta=[10 20 45 60 90]/180*pi;
t = [0:180]/180*pi;
phi =0:(pi/360):(pi/2);
Num_r = 50e3;
r = linspace(1,50,Num_r)./2;
col=['k' 'b' 'r' 'g' 'm'];
I0=1;Q0=1;U0=0;V0=0;
for i=1:length(theta)
    hold on
    for j=1:length(r_med)
        [P11(j,:),P12(j,:),P33(j,:),P34(j,:),Qsca_c(j,:),~,~] = ZK_W_Cloud_PhaseFunc(N0,r_med(j),sigma_g,N_ang);
        [~,indx] = find(theta(i)==t);
        F(j,:)=(P11(j,indx).*I0+((P12(j,indx).*Q0.*cos(theta(i)))+(P12(j,indx).*U0.*sin(theta(i)))));
      end
end

[Walter Roberson]

never compare floating point numbers for equality unless they are derived from the same array. No promises that any theta entry will equal t.

[John D'Errico]

Your formula lacks any use of the parameter V0. So where is V0 employed?

[Wiqas Ahmad]

These four parameters are constant. For the time being you just ignore it. The plot has nothing to do with the V0.