How to Delete a Discussion posted in open Group??? Please HELP

Hi there
If somebody could help me i would be very grateful!
I have posted a discussion in a Group (which contents are open) 2 years ago and I can't delete it.
Its coming up in every search engine and I am not happy about it.
I have emailed the administrator of the group who is a website and haven't checked in in this Group on facebook in almost 2 years, so obviously they either don't know the password or the staff there changed and no one knows about this group. In fact i haven't received anything from them.
How to do it myself????

Hello,

Unfortunately, the content posted there has likely been permanently archived by Facebook. Unless the post violated their terms of use Facebook themselves will not remove it. The only way therefore is by the group administrator(s)