Well, that's a dead end. The tablet has "unified storage," which is the norm these days.
Let's go back a few steps. When you connect the tablet via USB and you see that dialog box on your PC screen, instead of selecting anything, just click the red X to make the dialog go away. Wait a few seconds--does the SD card pop up next?
Also, after making those dialog boxes go away, open Windows Explorer and look at the device list on the left side--do you see the tablet there? Do you see a down-arrow next to it? If so, click it and see if it shows you Internal Storage and SD Card. This is how it works for my ZenFone 2 (I have Windows 10).
Another thing to try is to make sure the proper USB drivers are installed. They should be included in Samsung Kies, or you can find them here:
Download Center: Download Software, Firmware, Drivers & Manuals | Samsung