There are three standards of wireless internet in the world right now. type "B" type "G" and pre "N" (which is basically a fancier way of saying "G".
Now the nice thing about all three is they are all backwards compatible. Meaning that G and B can both work off a pre N router and vice versa. YOur dell will have a "G" wifi networking card built in. its speed is maxed at about 54 mpbs.
when you get your laptop all set up and ready to go you can have it detect and connect to any wifi "hotspots"
I am sure Japan will be loaded with them, if they arent, park yourself out front of a hotel. All hotels are set up with wirless internet for traveling business men.
I cannot see you needing anything. Its a universal product and everything should be golden.
Europe is back on baby!