Look for the GT-C3520 Firmware matching your region (e.g., C3520XXKJ7).
You cannot simply copy the flash file to an SD card. Feature phones like the GT-C3520 require a that communicates with the phone’s processor via a serial or USB protocol. The tool splits the firmware into chunks and writes them to specific memory addresses. samsung gtc3520 flash file and tool
Next, Alex put the phone in download mode by pressing a combination of buttons, and then he launched Odin. The software detected the phone, and Alex selected the flash file he had downloaded earlier. Look for the GT-C3520 Firmware matching your region (e