There are so many it’s hard to choose, but I think mine is:
Oh give thanks to the Lord, for he is good;
for his steadfast love endures forever! (1 Chronicles 16:34)
Here is a list to find your favorite:
Thankful Bible Verses
One verse I come back to often is Philippians 4:6–7
“Do not be anxious about anything, but in every situation, by prayer and petition, with thanksgiving, present your requests to God.”