I'd start at Pearl Harbor, you'll probably get told to patrol near Honshu, so it'll be a good idea to go via Midway and refuel there en-route. Sure it's a long way, but it'll give you time to play with stuff en-route.
Pick whichever you fancy sub-wise, but if you can manage it, get a bigger deck gun and stick it on the foredeck, also get the Aircraft warning radar, it could save you a lot of heartache. At this early stage in the Pacific war, you're likely to meet a few small single targets, and it will give you a chance to practice gun-laying without much of a chance at return fire.
Have fun
