Try selecting Tools > Upload Speed > 115200.
You might consider buying a USB to TTL serial adapter. It's much more convenient than trying to turn an Arduino board into an adapter. They are available from all the places you would purchase electronics components (eBay, Aliexpress, Amazon, Adafruit, Sparkfun, etc.) for a reasonable price. They most commonly use either the FT232 or the CH340 chip. It's a useful tool to have on hand. I prefer the ones that come with the "FTDI header" pinout:
- DTR
- RX
- TX
- VCC
- CTS
- GND
That is the most standardized pinout, which allows you to plug it right in to many boards (e.g. Pro Mini). Some have DTR and CTS swapped, but that doesn't matter. You will want one that allows you to select 5 V or 3.3 V.
