Sorry if I sound blunt, but it practically does not matter. Your mechanical HDD will NOT experience any difference between the two interfaces, so just plug it into any old sata port and don't worry about it.
If you are curious about which one it is, look on the sticker for the model number 7200.xx and search it up on google. That will tell you.
For the connectors, which motherboard do you have?
P.S. The ports look exactly the same - usually just coloured differently