I Am Building my pc at the moment but I can't seem to find where the power cable for my hdd on my psu.

Solution
Any of the SATA power connectors should work with that HDD. The power lead(s) are labeled and that unit has quite a few SATA power connectors. The connector must be properly oriented to the hdd to plug in: it only goes in one way. Don't force it.
Any of the SATA power connectors should work with that HDD. The power lead(s) are labeled and that unit has quite a few SATA power connectors. The connector must be properly oriented to the hdd to plug in: it only goes in one way. Don't force it.
 
Solution