Howler93,
The mine fields are in the stock game. If you have the map that came with the game.
Look at the legend and it tells you the different colors for the different years of the war. Fields are mostly around Japan.
If you don't have a map this link will take you to a site where you can download the map.
http://www.replacementdocs.com/download.php?view.4902
Also in Trigger Maru, Ducimus increased the density of the mine fields, the stock fields are not very dense.
Hope this helps!