K3b burning mp3s problem

[Josef Lowder]

After creating some mp3 audio tracks on my hp-xp laptop (gag ... because
I haven't figured out how to do this on my main Linux system yet) ... and
since the cd/dvd burner on my laptop seems to have flaked out ... I copied
the files to an SD chip and then copied them to my Linux box.  But when
I used K3b to burn a CD, the resulting CD does not play correctly.

It seems that in the process of burning, K3b changed the format from
mp3 to "riaa" (not sure of that type) or some other format that is not mp3.

How can I determine, for sure, what the format is of the files on the CD?
And how can I make sure that K3b burns the files as mp3 files?