Based on the level of respect or formality, you can say "Where in Korea are you from?" in Korean in 3 ways:

• Informal: gohyang-i eodi-ya? (고향이 어디야?), gohyang-i eodi-ni? (고향이 어디니?)
• Formal: gohyang-i eodi-yeyo? (고향이 어디예요), gohyang-i eodi-ipnigga? (고향이 어디입니까?)
• Very Formal: gohyang-i eodi-ipnigga? (고향이 어디입니까?)

- where: eodi (어디), eodi-e (어디에), eodi-eseo (어디에서)
- you (subjective): neo-neun (너는), dangsin-eun (당신은), dansin-ggeseo-neun (당신께서는), ne-ga (네가), ni-ga (니가)

Please refer to How to pronounce Korean Alphabet for the English pronunciation in this answer.