miten = kuinka

These words mean the same thing. Just in few expressions you can't use both of them:

e.g.: Anteeksi, kuinka? = Excuse me, what did you say?

In this example you can't say: Anteeksi, miten?

But in the most cases you can use both words:

Kuinka voit? = Miten voit? (How are you?)

'Miten' and 'kuinka' can be used as question words, but 'kuten' is never a question word. 'Kuten' means 'as' or 'like':

Suomessa on kaksi virallista kieltä, kuten tiedämme. (= ..., as we know).

Juna on myöhässä kuten aina. (The train is late like always.)