Thanks for replying.
Its not a think pad, its an idea pad. L340-15IRH . Here is a video of a YouTuber opening it up and installing a SSD
The model of HDD I am thinking of buying and installing is a SEAGATE MOMENTUS 500GB 2.5" (ST500LT012)
You can see the small socket to the right of the data connector and I wonder if this is for power and if it is then the type of cable I would need to get in addition to the data cable which I already have.