The best and recommended path would be to upgrade your license so you can start your community on the latest release. Which is not only more secure, modern, and stable in the sense of the software itself but likely going to be hard to find the insecure requirements to run PHP 5.6 and other corresponding server technology, which is out of support itself.
If you do go by finding it online, please note that is not legal, even if you have a license, as that is piracy. Not only is that illegal but pirated copies of software also have back doors, trojans, viruses, and the alike which will compromise your server, community, data, etc... causing more harm than good.
The only legal way to run the software would be if you had a backup of the files on your system. Otherwise, you need to upgrade your license and start your community on the latest release if you do not. If you have any questions on upgrading, please submit a contact request and we can help you.