STM32 - reading serial number on command line (with st-flash)
You have already read serial number, and far beyond it. You are not reading 32 bits, but 32 bytes from the starting offset.
You just need to understand how the Intel Hex format encodes data.
For instance, the serial number 0E513931 said by the ST-Link utility is the first 32 bits in the first dump file, it just reads 3139510E because that is how it is stored in the memory and then it goes on for the rest of the serial number bytes and the unused area is FF bytes.