Look at the meaning of each word:
Cómo - How
Adónde - To where (usually used for "to where" you go, example - to where to you go dancing, etc.)
De dónde - From where
Dónde - Where (usually used for "where" something is)
Which fits best with the answer (I'm from Cuba.)
How are you?
To where are you?
From where are you?
Where are you?
