UL requires a sticker. Perhaps it is on a side that you can't see.
If it really does not have one, I would plan on dumping the psu.
A poor quality psu that fails can damage anything it is connected to.
If your psu does not have a 6 pin pci-e power connector, it will not have the power to safely drive a graphics card that needs one.
It will be a 300w card, and probably less.
You might get away with a card as strong as a 7750 which does not need auxiliary power, but that's it.