Are these anywhere in Logos?
I found one in NPNF but I'm looking for some where he explained the Trinity which don't seem to be there...
I don't think so. You can find The Letters of Saint Athanasius Concerning the Holy Spirit (these are the ones where he explained the Trinity) on the Internet Archive:
http://www.archive.org/details/TheLettersOfSaintAthanasiusConcerningTheHolySpirit
The "Read Online" version is very nice looking. The OCRed text version there is awful, though. Otherwise I'd maybe volunteer to turn this into a PB. It would be a ton of work to make it readable. And I'm in the middle of another even longer one right now which is higher priority for me.
How to Ask for Help | Logos Wiki | My Machine Specs | My Blog
Rosie Perera: http://www.archive.org/details/TheLettersOfSaintAthanasiusConcerningTheHolySpirit
Thanks Rosie, that gave me what I needed.