Thank you for contacting Avenza Support! On Windows 10 devices, to access maps you purchased previously press the Account Icon (head and shoulders at the bottom left corner of the screen. Enter your username and password, and press Sign In. Once signed in, you can see the full list of the maps that you had previously added to your account. Select each of the maps that you want to download, then press Download in the bottom right corner. All of the selected maps will begin to download.
The screen you are seeing is if you try and access the maps from the Map Store through the app. To purchase maps from your desktop, go to: http://www.avenzamaps.com/maps/search and search for the map there. From that site, you can purchase maps, and add them to your account which can be download on your Windows 10 device.
If you have any questions, or further concerns, please let me know!