Do you have the from the sticker or the system menu to help narrow down the exact file? Firmware Update via USB Drive - Dahua Wiki
Use the Dahua ConfigTool on a PC to find the device on your network and push the update remotely. Download Firmware DVR 8CH DHUA 16MB rar
Log into the DVR’s IP address through a browser and navigate to Maintenance > Manager > Update . Important Safety Tips Do you have the from the sticker or
Once you have downloaded the file (often in a .rar or .zip format), extract it to get the .bin file. You can then update using these methods: making it unusable.
Installing the wrong firmware can "brick" your device, making it unusable.