How to convert SATA power port to Slimline power port
Use 2 5V wires and connect them to slimline (i.e. Pin :- 9, 10). Leave the third 5V wire.

Use 2 GND wires and connect them to slimline (i.e. Pin :- 12, 13). Leave the other four GND wires.

The SATA to Slimline converters available in the market only seem to use one wire for 5V &amp; one wire for GND. They bridge the two 5V &amp; GND at the Slimline side.

Using one wire for each is fine but I would recommend you to go with the 2-wire approach.