I have an airport router version 7.7.7. and was wondering if updates are still available

I don' have a Windows 10 PC here to check, but if you have an iPhone with AirPort Utility installed on the device or a Mac, you can apply the latest update for the AirPort, which was issued in June 2019.

Your current firmware.....7.7.7......was issued in June 2016, so you are long out of date, security wise.

Windows 10 disabled SMB1 communications.....which the AirPort use.......so it may not be possible to use the Windows 10 machine to apply any future updates. We'll have to wait to hear from one of the PC guys on that.

on airport utility 5.6.1 I can mark one of my airport devices in the left sidebar

then click the menu item called Base station in the top of the dialog

and choose upload firmware

but as mentioned the hd connected to my extreme is not something I can access from inside windows 10