Hi,does N68-VS3 UCC support Nvidia graphics cards?

Your motherboard alone won't be able to handle anything above a 1050Ti. Anything else needs external power connectors from your PSU.

You can't tell what the PSU is without looking at it. Almost every PSU, even OEM ones, have some sort of branding on them that will display wattage and show who makes them.
 


 
Power supplied, really. Your motherboard ONLY allows for 75W of power to flow to the GPU via motherboard. Any more requires an external power supply connector - if you are using a prebuilt machine, included OEM power supplies are usually low wattage, restricting upgrade room without upgrading the PSU as well, and might not have PCIe connectors for the GPU. If you're getting a 1050ti that doesn't need external power, you will be fine.