You have to buy a card pack to earn it yourself.
If you don't want to buy one then you can request card codes from the 39 clues.
there are instruction of how to get them when you ask in the help option.
There is something about sending an empty envelope with a stamp and name and sending it to some address. Try it
Here is one card code P2FHHNDHXP
the 39 clues most rare card code is P32979TXXP
a grate card code for the 39 clues is P32979TXXP
MANINBLACK and Hagia Sophia,P.S that's not the code. f4g3fdrckd
a 39 clues ultra rare card code is P247JJMMXP
this is a good code P36HTT2WXP
The code is: P2CN2PGGXP
p32979txxp and P3PPKN47XP
C2mt2kdnht caps
p24hjg3hxp
a wonderful card code is p32979txxp
it's the 39 CLUES and here is a code it is:P4C4M9DKXP
In the 39 clues what is the code for card 67?