[Plugin: WP Online Store] Customize automatic email messages

Hi there,

This is an absolutely brilliant plug-in! My client will be so happy with it. That is, if I manage to alter the automatic email message (which are sent after having created an account, ordering etc..)
I’m Dutch, so is my client, so these messages should be in Dutch as well. Translation is not the problem (I’ve been an English teacher) but finding the location is.
I’ve translated most of the (relevant) English php but that related all to the text on the site. I looked at some of the php’s below that, but they didn’t really gave me a clue as to which I should edit.
Some help would be very welcome.

https://www.ads-software.com/extend/plugins/wp-online-store/