You can download the package fedora-release-8-6.transition.noarch.rpm (from the update repo) or fedora-release-8-3.noarch.rpm (from the base repo of fedora 8). Check your rpm database to see which package you actually have installed. Then you can extract the content of the rpm package and copy the directory yum.repos.d in /etc.
# mkdir ./tmp
# mv fedora-release-8-6.transition.noarch.rpm ./tmp
# cd ./tmp
# rpm2cpio fedora-release-8-6.transition.noarch.rpm | cpio -dimv
# cp -pR ./etc/yum.repos.d /etc