How do I merge my gmail, icloud, outlook contacts all together?

Please use a web browser to transfer the data from Exchange account to another email account.

1. Try to export the contacts from google mail on a web browser. During Export select export as vCard and then log in to https://www.icloud.com using your Apple ID credentials Tap Contacts app > Settings > Import vCard.
2. You may use this --> Share contacts as vCards - Microsoft Support or Export multiple Contacts as vCards - MSOutlook.info and then log in to https://www.icloud.com using your Apple ID credentials Tap Contacts app > Settings > Import vCard.