The file is already extracted, just rename it to libstdc++-libc6.1-2.so.3:
In Slackware this lib is located at: /usr/i486-slackware-linux/ so I guess you have to put it in a similar place for your distro, or in /usr/lib. If that dir does not exist in your /etc/ld.so.conf add it.
cp libstdc++-libc6.1-2.so.3 /usr/lib
Mind that this maybe will not work as there are dependencies (other required libs, different compiler version) for installing a shared library. The best way is to find the right package for your distro containing that library and install it.