To get mines in you single missions you eed to ether install the mine mod from TDW or use OHII full or OHII environment.
Then when you load ME2 - add them using the sea folder and under environmental. As sober points out - use the chain maine 16m.
When placing them - just place one. Then select it and edit its settings in the left side tab.
Set speed to 0 - set it to novice and make it a docked ship.
Then copy it and paste new ones where you want them
