Divorce whomever of them you wish
Ghaylān ibn Salamah Ath-Thaqafi embraced Islam and he had ten wives from the pre-Islamic period of ignorance, and they all embraced Islam with him. The Prophet (may Allah's peace and blessings be upon him) commanded him to choose four of them
The Prophet (may Allah's peace and blessings be upon him) returned his daughter Zaynab to Abu al-‘Ās ibn Ar-Rabī‘ in marriage after six years without renewing the contract