Here is a link to a guide on how to complete all the missions in the stock campaign. All are right but the patrol mission. (the one you had) It says 100nm but I'm pretty sure it's 50nm. It's been a long time since I played the stock game.
http://www.subsim.com/radioroom/showthread.php?t=111509
EDIT: You did well getting the Uboat Missions. I never play the Uboats but most of the major mods are designed for 1.5. Now go sink some bad guys!
