In the dictionaries:
staff [countable, uncountable] the people who work for an organization
You say a staff member (or a member of staff in British English) or an employee, when talking about one person on the staff. ✗Don’t use a staff to refer to one person.
officer: someone who is in a position in an organization or the government
a prison officer
the chief medical officer
the organization's public information officer
The document must be certified by the proper officer of the state.
office staff: professional or clerical workers in an office
Let say, I am an average accountant mostly work in an office of an certain company.
Which of the followings are appropriate?
I am an office staff
I am an office staff member
I am an officer
I work in an office