You mean the Traditional Topology Tools for Manifold 8?
(Not, for example, the Business Tools extension, which includes Topology Factory.)
If you do want the Traditional Topology Tools, they available from the Manifold Free Stuff page. (Free and unsupported.)
Note that to install them on recent versions of Windows, you will need to launch an administrative command prompt (CMD with elevated privileges), navigate to the folder where the .msi file is located, then then use a manual Microsoft Installer command to perform the installation.
This command is for the 64-bit version.
msiexec -i Manifold-Traditional-Topology-Tools-126.96.36.199-x64.msi