Errrrr.... the audio format used by normal CD-DA is *not* mp3, but PCM at 16 bits/samples, 44100 samples/second. So you are definitely on the wrong way.
Anyway, to convert files from foobar2000 you must select the files you want, right click over them and then select Convert->Run conversion. Before that you must define the type of conversion you want (Right click, Convert->Settings). This will be "WAV (PCM, fixed point)" for files that are to be burned on a CD-DA.
Before proceeding I suggest you to get a grasp on basic digital audio technology reading the
Hydrogenaudio knowledge base pages.
Cheers
Sergio