I had a long reply typed up but the time out ate it.. so shorter version now that I've re-read your initial post and realize you want to use Moodle as an identity provider rather than service provider.
This plugin looks to be the only one that allows you to use Moodle as an IdP: https://moodle.org/plugins/auth_samlidp and yes, it requires Moodle 3.1 - 3.5, so Moodle 2.6 will not work.
simpleSAMLphp is not a moodle plug-in, it's a seperate program you install on the same server as Moodle.
So you need to either upgrade moodle, or find/write another plugin that will work as an IdP for Moodle.. or pay someone to do one of these things.
Upgrading moodle is probably the much easier step
This plugin looks to be the only one that allows you to use Moodle as an IdP: https://moodle.org/plugins/auth_samlidp and yes, it requires Moodle 3.1 - 3.5, so Moodle 2.6 will not work.
simpleSAMLphp is not a moodle plug-in, it's a seperate program you install on the same server as Moodle.
So you need to either upgrade moodle, or find/write another plugin that will work as an IdP for Moodle.. or pay someone to do one of these things.
Upgrading moodle is probably the much easier step