Based on the level of respect or formality, you can say "I am a herdboy." in Korean in 3 ways:

• Informal: na-neun mokdong-iya. (나는 목동이야.)
• Formal: na-neun mokdong-iyeyo. (나는 목동이예요.)
• Very formal: jeo-neun mokdong-imnida. (저는 목동입니다.)