No. You will not have the power connectors the RX580 requires and using adapters would likely overstress the psu possibly causing damage.
It has the cables but its some oem unbranded psu and i guess it would be sketchy even trying to run the RX 580 on thatNo. AMD recommends a minimum high-quality 500 Watts PSU for the RX 580. That won't be sufficient to power up the entire rig using a 300 Watts PSU. But which power supply model is it ? Does it come with any PCI-cables for the GPU as well ?
I really doubt that a 300w psu has both an 8 pin and a 6 pin aux pcie cable that the RX580 requires.It has the cables but its some oem unbranded psu and i guess it would be sketchy even trying to run the RX 580 on that