There are many Psalms that capture the gratitude that Thanksgiving is centered on. Perhaps none better than Psalm 100.
If you are stuck today on how to pray before your Thanksgiving meal, I offer this as a way to do so. Have a wonderful holiday! We are finished with Luther's catechism, and next week we'll begin with our Advent theme: The Coming of the Light
A Psalm of thanksgiving.
Make a joyful noise to the Lord, all the earth. Serve the Lord with gladness; come into his presence with singing.
Know that the Lord is God. It is he who made us, and we are his; we are his people and the sheep of his pasture.
Enter his gates with thanksgiving and his courts with praise. Give thanks to him; bless his name.
For the Lord is good; his steadfast love endures forever and his faithfulness to all generations.