how do i locate all devices connected to airport

How is your Brother printer connected to the AirPort base station? By USB, Ethernet or wireless? If it is connected by USB, then the printer should show up in the AirPort Utility as the base station is performing as the print server. Also, which exact model of the AirPort base station that you have? ... and how is it being used in your current network? That is, is it the only router in the network or is it configured to join an existing wireless network as a client?

Were you able to access the printer from your Windows computer before and this just started happening or have you never been able to successfully access it?

Since your printer is connected by wireless it is performing as the print server, not the AirPort base station. That would mean that you need to make sure that it is properly connected to the wireless network using either the printer's administration software or its front control panel. I would suggest that you access the Brother online support site for the steps needed to do so. Please post back when you have verified this.