You ask, “Where does Qur’an say previous Messengers had multiple wives?”
Isn’t this a silly question for one who claims to be a student of Qur’an Alone? Especially in view of the fact that Prophet Abraham (peace be upon him) was inspired by God to use “the natural laws and forces of the heavens and the earth” to establish the Deen.
Hence, all Prophets who took more than one wife “followed the Creeds of Abraham”. There was nothing in the Creed to stop them to do so.
Therefore, in this context, if the Bible stated that some Prophets took multiple wives, I would not doubt it.
Likewise, in the context that God stopped Prophet Muhammad (s) from having more than 11 wives, I would say 70 or 700 wives for Solomon in the Bible might be an exaggeration but not 7.
I think you deliberately ask such questions to kill discussions that do not suit your ideologies.
AK Sayed (South Africa).