[malaguti]

I would like to ask how much moving average should I use if the chart is changed to a monthly chart? Thank you!

Stan doesn't go into this in his book. you could argue you should be using the same periodicity, ie 10 and 30 (trader vs investor).
However i find the monthly is now even less erratic in terms of price action and a lower average generally suffices. 
The 30 month way too slow and the 10month would keep you out of a lot of trouble. Like i say that's my preference for the monthly