This is a step by step tutorial showing how to extract an nb0 firmware. nb0 is the file format used by certain OEMs such as Nokia HMD e.t.c for their firmwares
Launch the nb0_tools_FIH_Mobile tool by double clicking on the executable file
Click "select nb0 file"
In the new window that opens, select the nb0 file you wish to extract then click "Open"
It'll list out the contents of the nb0 file, click "Unpack"
In the new window that opens, select the folder when you wish to save the extracted files and click "OK"
The extraction process will begin and you'll notice the progress bar moving. The tool might lag for several minutes so ensure to wait until extraction is complete
Once complete, a new window will open that reads "Done!", click OK
You can close the tool and open the folder where you saved the files to view the extracted contents