Buy this: https://www.amazon.com/Prong-Standard-Speaker-Monitor-Replacement/dp/B09YWNYDYG/ref=psdc_597260_t3_B08SJ2LRZJ

Or maybe you have one of those cables lying around.

The side of the adapter is just a normal 'C7' socket, used by many devices.

looks like you'll need a cable with a c8 plug, like this