H4 Visa already Expired. Should I file New H4 or file I539 for Extension of H4 visa


My H4 visa was valied till March 2015. My Husband is in US on H1B and recenetly got his visa transferred to New Employer. His visa is valied will 2018 In this case, Do I fresh file a New H4 Visa Or I539 for extension to H4 visa.

Please help urgently