"It is 10000 yen."
The way I figure out 万 is draw an invisible line four digits to the left. Now look at the left side and ignore the rest for now. If it is 10000 then you would draw the line between 1 and 0. On the left there is only 1 so you have 一 and because it is a million you add 万. If you have something like 12340 then we would have 一(because the line still draws between one and two) 二千(for the number of thousands there are) 三百(for the number of hundreds) and 四十円（for forty yen) all together it would be 一万二千三百四十円. I hope that helps some