Reddit mentions of Trueway 6 Pin PCI Express Power Adapter Cable to 2 x Molex LP4 Lead

There are adapter like this that can help:

https://www.amazon.co.uk/Trueway-Express-Power-Adapter-Cable/dp/B008AS7660/

They sometime came with the video card, but most modern card don't came with those anymore.

I would not use any 8-pin adapter - too much current (150W) to consider safe to use with old power supply.

http://www.amazon.co.uk/gp/product/B008AS7660?keywords=molex%20to%206pin&qid=1450026350&ref_=sr_1_2&sr=8-2

Okay, thanks, final question though :) Is that adapter the correct one? It looks like it only have 3 pins in it whereas the molex pin has 4?

My main case fan only comes in molex, so do I need to buy an adapter like this to plug it into my PSU?

The RX 480 only draws around 150w, which isn't a huge amount. You should be fine I'd say with any PSU 400+w. As another member said, you can get a dual molex to 6 pin pci that looks like this.

If you can list the PSU you have in the build, myself or someone else will be able to tell you if the PSU comes with the PCI cable or if an adapter like that will be needed. If the PSU is only 400w or even lower, it would be ideal to list all your parts, so someone can check you will have enough power available.

Worst case you may end up needing a new PSU, something like this 500w EVGA bronze 80+ is reliable, should cover your power requirements (depending on other components, but I'd be surprised to find otherwise) and not overly expensive (£57) for what your getting.