Translation:Do I need my passport when I go to Slovakia or to Poland?
- v + locative, e.g. ve škole, v Praze, v Česku, v Americe
- na + locative, e.g. na ulici, na stole, na zemi, na Duolingu, na Moravě
- do + genitive, e.g. do školy, do Prahy, do Česka, do Ameriky
- na + accusative, e.g. na ulici, na stůl, na zem, na Duolingo, na Moravu
This is just something that has to memorized. Just like you have to learn when to use "in", "on" or "at" with different places in English. In Czech, some places take "v + locative" for position and "do + genitive" for direction. Other places take "na + locative" for position and "na + accusative" for direction.
Most countries take "v" and "do". The once that take "na" are especially islands. Slovensko is special probably because it's considered more a region than a country (could be because of Czechoslovakia).
- na Moravě - in Moravia (part of Czechia)
- but: v Čechách - in Bohemia
- na Slovensku - in Slovakia
- but: ve Slovinsku - in Slovenia
- na Islandu - in Iceland
- na Maltě - on/in Malta (both are used in English)
- na Zemi/Marsu/Venuši - on Earth/Mars/Venus - planets take "on", too :)