Saint Tikhon when he was Archbishop of the Russian Church in North America approved this service for Orthodox Christians to celebrate the American Thanksgiving Day. In doing so, He took an American Holiday and made it a Liturgical Holy Day. Even if this service is not used in your own parish (My current parish does not serve it), it has become the service we do in our home during American Thanksgiving as part of our prayers for Thanksgiving day.
This website has the service:
http://www.orthodox.net/services/thanksgiving_moleben.html.
I hope you will enjoy reading it and praying it to enhance your home celebration of Thanksgiving Day.
Please note that while many will say it was written by St Tikhon, Enlightner of America, he just approved a translation of the Slavonic Moleben into English and commended its service on American Thanksgiving Day.
Thomas
Convert Issues Moderator