If a town becomes a city under this chapter, the circuit court having jurisdiction over the city shall appoint for the city an electoral board of three members, the term of one of whom shall expire on the first day of the following March, the term of another to expire one year later, and the term of the third to expire two years later than the term of the first. The court shall at the same time, if necessary, appoint one sheriff, one attorney for the Commonwealth and one clerk of the circuit court. The terms of all officers appointed by the circuit court shall expire when their successors are elected or appointed and qualify, pending the next ensuing general election or, if the vacancy occurs within 120 days prior to such election, pending the second ensuing general election.