What you see is actually the Internal Storage. For most of the available phones, the SD card is actually the internal storage, that's why the antivirus scans it. You shouldn't worry about it. If you connect an actual SD card, the phone will either see it by its ID, something like ABCDE-1234 or by External SD Card.
You can continue using the antivirus you already have as it's normal to show SD card instead of the Internal Storage.