Hello Steven,
To display decimals point you can use xtickformat and ytickformat for the x and y axis, respectively. Also, you may want to remove the exponent from the axis.
f = figure;
ax = gca;
x = linspace(0, 1e3);
y = linspace(-3, 3) * 1e-3;
plot(x,y);
% Set format to decimals
ytickformat('%.3f');
% Remove exponent
ax.YAxis.Exponent = 0;
