Let me save you some time. DON'T TRY IT!
What do you want to do with it and what PSU
Ah, Houston, we have a problem and we don't have any duct tape:
Okay everyone, put down the screwdrivers and RUN!
Not only is this system "brick" powered, but there is no provision for adding a normal desktop PSU because there are no PSU connectors on the motherboard other than that DC connector! Looks like this system comes with either a 90 or 120 watt PSU as they never intended to handle more than the following GPU's:
NVIDIA® GeForce GT720 2GB
AMD® Radeon R7 240 2GB
NVIDIA® GeForce GT730 2GB
AMD® Radeon R5 235X 1GB
Intel® HD Graphics
NVIDIA® GeForce GT740 4GB
NVIDIA® GeForce GT710 1GB
NVIDIA® GeForce GTX745 4GB
The TDP of the GTX 745 is 55 watts.
You
might be able to install a GTX 1050 (NON Ti)
that does not have a power connector, but
the power brick would have to be upgraded as well.
Useful TouTube:
Asus K31ADE - An Overpriced Asus Desktop Computer Powered By A Laptop Charger