There is no specific 200mb card. You just get a new T-Mobile nano sim. You stick it in the iPad Air/Mini Retina, then you activate it. You either activate it as a pre-paid plan or post-paid plan.
If you activate it as pre-paid, you do not have to provide any billing info. All you provide is your name, email, and birthdate. You get the free 200mb for the life of the tablet every 30 days.
If you activate it as post-paid, you can also choose the free 200mb, but for billing purposes, it attaches to your voice plan or existing T-Mobile account. Even if you have an existing T-Mobile account, you do not have to activate the free 200mb as post-paid. You can set it up as pre-paid and keep it entirely separate.
I believe the $10/month for 500mb is if you are post-paid and have an existing T-Mobile plan. It is normally $20/month for 500mb, but if you are post-paid, you get a $10 discount, making it $10/month instead of $20.
Okay, that was super helpful! So I don't end up talking to the wrong person and get the run around once again, let me ask you, does the T-Mo Nano Sim cost anything? How do I do this, do I order from their website or call them to get one? It's funny how the T-mo CEO does all this chanting and their employees don't understand how to sell their product to prospective customers.