STM32F407 is read protected by Level 1.
You can connect st-link to read, but you have to lower level to 0, If you do this you gonna erase all device.
I got for couple of days good vxdiag from my friend and i trying to get bootloader from MCU.
To connect st-link:
First upper gold pin from the left are pins for SWD: GND, SWDIO, SWCLK, VCC.
Lower pins: VCC, TX, RX, GND
I`d change my MCU for new one, but need also full dump.
Some usefull informations: