Based on the level of respect or formality, you can say "When will you graduate?" in Korean in 3 ways:

• Informal: neo-neun eonje joleop-hanni? (너는 언제 좋업하니?)
• Formal: dangsin-eun eonje joleop-hanseyo? (당신은 언제 졸업하세요?), dangsin-eun eonje joleop-hapnigga? (당신은 언제 졸업합니까?)
• Very Formal: dansin-ggeseo-neun eonje joleop-hasipnigga? (당신께서는 언제 졸업하십니까?)

- when: eonje (언제)
- to graduate: joleop-hada (졸업하다)
- 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.