That is just a prepaid card to add $30 to your T-Mobile account. It isn't needed for the $30/month plan.
What you will need is a T-Mobile Monthly SIM Kit. The cheapest place to get that is from the T-Mobile website
, though you can also get them from T-Mobile stores (typically are around $10 in the store). Once you have the card and are ready to activate, just activate online and have a method ready to add money to your T-Mobile account (prepaid card or credit card).