I think you go upstairs of the Pokemon center and you get a friend and link cable (you can only trade using gameboy SP, and the gameboy that came out before SP)then you talk to one of the ladies and one of them will say something about the trade room and then you and youre friend will trade Pokemon and youre kadabra(after trading) will turn into an Alakazam and if you cant go upstairs I'm guessing you have to beat the game or get like 5 gym badges or something.
Otherwise you cannot get an Alakazam there is no one in-game that offers to trade a Kadabra unfortunatley. Sorry
Hope this helped :D
