You should decide "what" and "how" do you want to store. You can't store five snapshots in one *.png image. You can store this data (your workspace variables) in *.mat (better choice) format https://www.mathworks.com/help/matlab/ref/save.html, or save it as a five different *.png images.
p.s. In your code there are some mistakes! if you wouldlike to save five snapshots from webcam to a different png files you should use this code
wblist = webcamlist;
cam = webcam(wblist{1})
for i=1:5
filename = sprintf('myimage%02d.png', i);
imwrite(snapshot(cam),filename);
end
