yum uses RPM, so the following command will list the contents of the installed package:
$ rpm -ql package-name
Not in Linux at the moment, so can't double check, but I think it's:
rpm -ql ffmpeg
That should list all the files installed as part of the ffmpeg package.
I don't know about yum, but rpm -ql will list the files in a particular .rpm file. If you can find the package file on your system you should be good to go.
rpm -ql