Do you mean Millainen maa Viro on? vs. Millainen maa on Viro?
The grammatical case system liberates the word order in Finnish, so both questions are grammatically correct. Compare this to English which is almost exclusively a subject-verb-object (SVO) language. However exposure to the Indo-European languages (mostly to germanic languages and Russian) has led to that, that the SVO order is the most common one in contemporary Finnish too.
A notable exception is, that we haven't adopted the reversed word order in questions.
- The teacher told us what kind of country Estonia is. (the subclause is an indirect question that uses the normal SVO order)
- What kind of country is Estonia? (a direct question uses the reversed order)
- Opettaja kertoi, millainen maa Viro on.
- Millainen maa Viro on?
That's the normal, neutral word order. If you use the reversed word order millainen maa on Viro, you're emphasising, as if you were comparing it some other country. Say that to an Estonian (who will fully understand the phrase) in a bar without immediately praising his/her country, and you will get a malevolent glare.
(I'm native Finnish speaker)