Configuring PR4100 for access in Office 365 environment

I have a PR4100 that I’m trying to access on a Windows 10 machine. My primary user account is “AzureAD[user name]” After some discussions with a Microsoft technician, I realized that the Azure AD was my problem. This was confirmed by creating a local user account on my machine, which allowed me to access the NAS without issue. It seems then, that I need to set up the NAS to use Active Directory.

The inputs, however, have me a bit stumped. I’ve found the instructions about getting into the dashboard, but the following four entries just keep getting me a PrincipalNames error.

I’m being asked to input the following info:

User Name: Is this my full account log in (“AzureAD[user name]”, or some other variation?
Password: I presume this is my user password for the account corresponding to the User Name
Domain Name: My domain is being run through Office 365, so is it my actual URL, or some MS variation?
DNS Server: One that has stumped me. It appears to want the IPv4 address, but I’m unsure where to find it. The system wants to autopopulate with my router gateway ID, but that seems wrong.

Any guidance would be appreciated!