How to plot 3D surface of an equation ?

I have some constant values and an equation. i need to plot as 3d surface. the data as follow,

neeta = 0.75; I = 100; U = 10; r = 10; R = 6; q = (3.*neeta.*I.*U ./ pi.*R^2) .* exp(-(3.*r^2 ./ R^2)

this equation is to represent the heat flux distribution over a circular region. i need to visualize a bell shape surface over a plane to fin the intensity.

[Yu Jiang]

It seems that you would like to have q as your z-axis. What are the variables you want to specify as the x-axis and y-axis? And what are the ranges of them?