몇 means ‘how many’ but when used with 번 together, the meaning of 몇 becomes ‘what’ or ‘which’.
‘몇 번’ is normally used to ask a question which involves the answer to be in numbers e.g. telephone number or bus number.
In this case, we will answer using Sino-Korean numbers.
We will normally attach ’예요/이에요?’ as the ending when ’몇 번’ is used.
Ex1)
Q: 몇 번 버스예요? (What is bus number)
A: 502번 버스예요. (It is number 502)
{502번 is pronounced as 오백 이 번 in this case because we are using Sino-Korean numbers}
{번 means number}
{버스 means bus}
{As 버스 is a noun and ends in a vowel, we will attach 예요 to it}
Ex2)
Q: 전화번호가 몇 번이에요? (What is your telephone number)
A: 224-2243이에요. (It is 224-2243)
{In this case, ’224-2243′ is pronounced as ‘이이사에 이이사삼’ because we are using Sino-Korean numbers and the ‘-’ is pronounced as ‘에’ when using together with numbers}
{전화번호 means telephone number}