i was wondering how i could transfer iced cake to a card board platter with out it falling apart. thanks

If it's in the fridge and the icing is hard it will be a lot easier. Do you have to take the cake off of a board that it's already on completely? It can be done, but really, make sure the cake is totally cold, like in the fridge overnight cold. Run a spatula around the base of the cake to break any seal that formed with whatever it's on, then slide a large spatula under it, or better yet something like one of those flexible cutting mats that's thin plastic and you can slide underneath it to lift it in one piece. Work carefully!

I'll add that I wouldn't try this with a cake that's any larger than about 10" across, and I've been doing cakes for 20 years. So if it's the first time you're trying it I wouldn't do it with anything larger than about an 8" round!

The only other suggestion I have is to keep it on whatever it is already on the just glue that to the new board.   If what it is on now is bigger than the cake (such as a 10" cake on a 12" board) cut off the extra as close to the cake as you can get.  Pull the cake to the table edge and run a sharp knife into the board as close as you can get it and then all around.   I've seen this done by someone who make all their wedding cakes this way.  It's one of those things that words do not really paint a good picture of;)

You could flip it over (I use an acrylic board with parchment on it), switch the board, then flip it back. Chilled of course.

I would use a cake lifter; it's a purpose made tool for that very situation. Mine is 10 inches (about 25 cm) in diameter with an offset handle. 

Re the comment by costumeczar, if you haven't done this, then please, in future, attach your cake (permanently) to a cake card before you start working with it. Then, any lifting is under the card rather than directly under the cake.

I hope all goes well.