Look for the "Hardware Version" on the sticker at the bottom of your router (e.g., vA1 or vB1). You must match the firmware to your specific hardware version to avoid "bricking" the device. How to Update Your DSL-3890 (Step-by-Step)
To ensure a successful update and avoid making the device inoperable, follow these safety guidelines from : DSL-3890 - D-Link Support Resources dsl3890 firmware link
To keep your D-Link DSL-3890 AC2300 modem router running at peak performance, it is vital to keep its firmware updated. You can find all the necessary firmware files and official documentation on the D-Link Australia Support Page Direct Download Links Look for the "Hardware Version" on the sticker