Please follow the flow of the conversation. Jumping up then down, then up
again makes a conversation hard to follow. I've reordered your message this
time.

Codecs are used by particular programs. *If* there are additional codecs
available they should be on the site that provides the program. Not all
programs are written to use external codecs, and codecs may not be written
even if the program can handle them, so there may be none for whatever
program you use. Some other sites do provide codecs. Can you guess what web
searches are for?

You haven't said what the codec is called- it will have a name. It will also
have a purpose and it may be that other programs provide that functionality
without add-ons. You haven't really given any details to allow anyone to
help except that rather than give general advice, but my advice would be to
look for and download a program to play your files.
There can be many codecs for a particular file type as the coding is altered
(or improved) over time. Knowing the program you are using and the codec
name and/or particular type of decoding it needs to do is essential to get
the right codec. And knowing the file extension probably won't be enough to
find the right one, except by chance. You need the encoding type.