Yes, those icons come from Ubuntu itself (or some other system package). They (unfortunately) override any Inkscape icons, both custom and default, that users can install on Linux Mint. (I hate them, but can't get rid of them - I would like to use the 'symbolic_icons.svg' file from the /share/ directory, but can't, because they broke it by adding their own icons...)
Anyway, yes, those icons you have there come from /usr/share/icons/Mint-Y/actions/ . You can proabably copy them over to your Windows machine - not sure how to, and if it's necessary to, change the load order. It's not one single file, but these are icons that come with the system, they are separate files.