I bought this landline phone about 2 years ago. At that time I didn't need an extra cable. One is always included and most of the time it fits.
But the question is whether it has to be plugged directly into the wall socket or whether you want to connect it to the router, the modem, for example, as is common today (VOIP).
I would first find out the target socket, take a photo if necessary and contact the manufacturer's customer service directly. Then you play it safe.