Mission USS (of all types) are specific. You can find them either by using the new FSS and zooming in on the USS in the system until you come to the mission specific one (it will be identified as such), or you can drop out at the system nav beacon and scan that, at which point you will get a mission update in your HUD and the mission specific USS will be highlighted in your left HUD navigation panel.
To scan the nav beacon, make sure you target the actual beacon, not it's HUD marker, point your ship at it and it will passively scan. Easiest way to target the physical beacon is to select it from the Contacts tab in the left HUD.
