なんて幸せそうな顔なんだ

Meaning
what a happy face you have

Vocab used in this sentence

なん
what, how
the, it, have
幸せ
happy, happiness, happily
そう
so, really, yes, right, that's right, i see, indeed, seeming
a, the, na, nan, nai
face, look, expression, features, countenance
a, the, na, nan, nai
i, n, m, ng, yin, hmm
is, be, are, am, it is, seems