Not sure what you want with the firmware but as janch says Garmin Express downloads it to your PC and updates your device.
9.70 is the latest version, if you updated your device yourself then look in
C:\ProgramData\Garmin\CoreService\Downloads\PrimaryFirmware\PrimaryFirmware_PrimaryFirmware.006-B3061-00.9.70\gsup\006-B3061-00\9.70\full

This firmware is encrypted so not recognized
Firmware version as specified in GCD file: 9.70 for Unknown device (HWID 3061).
File format not recognized.