Are your xbox's chipped? If they are I recommend using Xbox-Saves Manager. It is a wonderful app that will give you the names of each game and compress them while transfering.
Otherwise your savegames are in the UDATA folder on E:. If you look in it you will see folders like e045395d92 and by that you are supposed to know wich game it is...
If only one of them are chipped use a memory pack to transfer them.