How can I fix this?

Hello guys. I’ve just installed k3b but after starting it, it welcomes me with the following warning:

                                                          MP3 Audio Decoder plugin not found.
K3b could not load or find the MP3 decoder plugin. This means that you  will not be able to create Audio CDs from MP3 files. Many Linux  distributions do not include MP3 support for legal reasons.

*Solution*: To enable MP3 support, please install the MAD MP3  decoding library as well as the K3b MAD MP3 decoder plugin (the latter  may already be installed but not functional due to the missing libmad).  Some distributions allow installation of MP3 support via an online  update tool.

I’ve tried looking for the package but I couldn’t find it. How can I fix this?

Thanks in advance for the help,

Which openSUSE Version is running on you PC?

And on that, see the first Threads here:

it seams you are running an extremely old version of opensuse and k3b as the mp3 patents have ended and now the mp3 plugin is bundled with k3b
if you are using 13.x you will need to add the packman repo for that version and do a full vendor change to it
what’s the output of

cat /etc/os-release

you really should install a current release not an unsupported one