Pixhawk Firmware Backup

Dear all
I have a pixhawk with a unknow firmware. The smal company who sold me the uav is closed now and I need a backup .
I did a parameters backup, but is very important to me, the complete firmware backup.
Some body could help me in this task?
Thanks in advance,

@BobJ see MP’s message tab for detail:

chances are your firmware is available for download if it is an ardupilot default one.

if it happens to be a customized firmware and / or its source not accessible anymore, you can do a full MCU storage backup using STM flasher utility.

Dear Friend, tks for the response.
It is a customized firmware and the source is not accessibile anymore. So i must DO a backup of it.
I´m trying to use the STM Flasher utility, but it says that can not recognize the device.
My device is a pixhawk 2.4.8 ( STM32F427).

Do you know where can I find a tutorial to connect pixhawk and STM flasher utility?
thank you again

info is right on the page i linked above:

…communicates through the RS232 with the STM32 system memory bootloader.

that means you need to put your FC into boot0 (=DFU) mode and connect via UART with an FTDI.