Check CFG folder from "NSS_Uboat7c41". If in Cfg folder is something like this:
[Unit]
ClassName=SSTypeVIIC/41
HumanPlayable=NO
;;Interior=data/Interior/NSS_Uboat7/NSS_Uboat7
UnitType=200
MaxSpeed=17.0
MaxSpeedSubmerged=7.6
Length=67.4
Width=5.3
RenownAwarded=130
Then it is folder for the U-Boat which is generated by the game, not human playable.