The triad above is in its

The key signature has one flat (B_b), indicating F major or D minor. The three notes of the triad from bottom to top are D, F, and B_b.

Rearranging these notes in root position gives B_b-D-F, which is a B_b major triad. In root position the notes would be stacked B_b-D-F, with B_b as the lowest note.

Since D (the third of the chord) is in the bass instead of the root, the triad is in its first inversion. First inversion places the third of the chord as the lowest sounding note, producing the intervallic arrangement of a third and a sixth above the bass.