I don't understand it came to this. I thought it was explained in the first 13 Replies that the DB9 was to connect to your device because you said it had a DB9 FEMALE which is why you selected a DB9 MALE connector on the RS232 to TTL converter.
The plan was to connect your device to the DB9 and connect the TTL out from the converter to the Software Serial pins 2 & 3
and use the arduino serial (0 & 1) to echo the data received from black box using serial print statements.