There are 3 things to consider:
- Size: your case is a low profile case: it's slimmer than a regular case, and only low profile cards will fit in it. That will limit your choice to entry level GPUs (which is OK because the rest of the computer is also entry level, so it it will stay balanced).
- Power: i can't seem to find information about the power output of the computer's power supply unit (PSU), but i can imagine it will be quite low, maybe 250W. Some GPUs (even some low profile) require extra power from the PSU, which is provided via a PCIe cable. I imagine your PSU does not have any such PCIe cables (https://www.google.es/search?q=psu+pcie+cable&client=firefox-b-ab&dcr=0&source=lnms&tbm=isch&sa=X&ved=0ahUKEwj9xtDUpP_YAhXJXBQKHRFXCTYQ_AUICigB&biw=1920&bih=1126), so you will need that, besides being low-profile, your new GPU doesn't need additional power
- Price: right now, there's a cryptocurrency mining craze going on. There's very limited availability of GPUs, and prices are very inflated. It's a bad time to buy.
If you still want to go ahead, see here the recommendations from Tom's Hardware:
http://www.tomshardware.com/reviews/best-gpus,4380.html
Personally, considering the rest of your PC, i would not buy anything over a GT 1030, because it's so expensive right now, and because it won't be able to strech its legs with the CPU you have. So try to find in your prefered store a low profile GT 1030 (this model does not require extra power), and go for it.
Hope this helps!