STM32L4 example available in X-CUBE-BLEMESH1 is for NUCLEO board. Is there any ready example code for this B-L475E-IOT01A2 to test BLE Mesh?. If it is available please share.
If you follow this approach, please make sure that you update the x_nucleo_idb0xa1_targets.h file to use the correct pins for your board.
Another alternative is generating the Virtual_COM_Port project for the board with STM32CubeMX and then use the FlashUpdaterTool utility (included in the X-CUBE-BLE1 package) to perform the update.
I would go for the first option. If you have problems, I can generate a binary for you.