It's a priority motherboard that uses a 90 watt laptop power plug.I looked at the Currys web site and it shows the Asus K31ADE used a 300W PSU. It's listed as no longer available (obsolete).
I don't know of many desktop computers that will run on a 90W PSU, apart from a few small NUCs. How big is the computer case?
If you upload a selection of photos with the lid removed, we might get a better idea about upgrade options.
As JohnBonhamsGhost said, it might be better to get another PC.