Cheap MIDI <-> USB adapter hacking

Hello, for all that understand a bit more than me, here's a nice link on how to hack a nice cheap adapter to power your Arduino and send midi via usb.

But for me and all who dont understand that much. Could someone explain how can i make the same hack, but with a slightly different adapter. My adapter has the same name and almost the same look, but when i open it it has no headers, just holes where wires are soldered.The holes are as follow:
O+ (MIDI IN cable was here)
O- (MIDI IN cable was here)
G (NOTHING was here)
G (NOTHING was here)
I- (MIDI OUT cable was here)
I+ (MIDI OUT cable was here)
The MIDI jacks have labels on them IN and OUT. As i understand, when i want to output MIDI from the arduino i should connect it with the IN midi jack. The MIDI IN jack when followed to the circuit board has only 2 wires which are soldered to hole O- and hole O+ on the PCB. The cable is shielded, though the shield is not soldered to the GND hole in the PCB. The jacks are cast (I cant take the jack off and replace wiring aka i dont know those 2 cables to which pin of the DIN 5 Jack are soldered) The tut i linked above says that i should connect V from the USB end with Vin on the arduino.
My questions are:
Can i use the already given MIDI cable to hack the device like in the tutorial?(My MIDI cable has only 2 wires
If not where should i attach the TX pin should it be to O+ or O -?
Thank you very much and i hope that that tut would help you

As i understand, when i want to output MIDI from the arduino i should connect it with the IN midi jack.

I would think that the OUTPUT from the Arduino would go to the MIDI OUT plug which I expect is normally plugged into the MIDI OUT jack of an instrument. This plug is wired to the I+/I- holes because the OUTPUT of the instrument is the INPUT to the converter.

If your MIDI-to-USB has six holes on the MIDI side I would wire it just like the diagram.

Hole 1 (nearest the LED) through 220 Ohm resistor to +5V or Arduino.
Hole 2 to TX on Arduino
Hole 3 to Ground on the Arduino

If you want to power the Arduino from the USB cable you will need to connect the +5 pin of the USB side to +5V (not Vin!) on the Arduino. Note: The 5V from USB is not sufficient for the Vin pin which needs 7V or more.

thank you for the answer! i hope this answer helps not only me but other people too