The easiest way is to use stem3 because it locates the points it displays:
Age = [10 7 8 9 5];
Volume = [1000 950 800 1500 600];
Quantity = [1.3 0.8 2.4 2.6 3.1];
figure(1)
stem3(Age', Volume', Quantity')
grid on
xlabel('Age')
ylabel('Volume')
zlabel('Quantity')
