Micsoft Windows 10 has a native password manager and as a consequence so does Microsoft's Edge browser.
Your passwords are stored within "Credential Manager" Web Credentials here.....
Control Panel\All Control Panel Items\Credential Manager
I need it to work together with a iPhone 6.
That is probably going to be a deal breaker as Apple and Microsoft are not necessarily known for their cooperation or interoperability.
That would likely require some third party addin and I do not know of any that are out there..... yet.
It's still early days and Edge doesn't support much in the way of extensions or addins but it is early days and there are some interesting rumors about changes that are coming for Microsoft's newest browser offering.
Have you considered experimenting with Safari (Apple's browser offering) to see if it may have the feature you are looking for to work with your iPhone?