How can one use 二週間 to say, "In two weeks from today, I am going to Tokyo."
I am confused on how one would use particles here and I need some help.
If it were me, I would say
I don't think 後 is usually considered a particle (助詞).
二週間 = a duration of two weeks. So you need to express after that duration has passed.
Two other ways to say this:
The verb する in the first one is roughly equivalent to the verb 経つ in the second one, and both mean "to pass time".