Мой отец работает в офисе.

my

Breakdown of Мой отец работает в офисе.

• в: in
• работать: to work
• офис: the office

Questions & Answers about Мой отец работает в офисе.

Why is it мой отец and not моя отец or моё отец?

In Russian, possessive pronouns like мой / моя / моё / мои must agree with the gender and number of the noun they modify.

• отец (father) is masculine, singular, so you must use мой.
• моя is for feminine singular nouns (e.g. моя мама – my mother).
• моё is for neuter singular nouns (e.g. моё окно – my window).
• мои is for all plurals (e.g. мои родители – my parents).

So: Мой отец работает в офисе. is grammatically correct because мой matches masculine отец.

What’s the difference between отец and папа?

Both mean father, but the tone and usage are different:

• отец – more formal, neutral, “father”.
  Often used in documents, official speech, and more formal contexts.
• папа – more informal, emotional, “dad / daddy”.
  Common in everyday family speech, especially by children.

Your sentence could also be:

• Мой папа работает в офисе. – My dad works in an office.

Same grammar, just a different level of formality.