Presuming that the table top phone is not an antique, (older than 30 years), the "speaker" in the hand set normally would be with an impedence >= 32Ω, and the PC should be able to drive it sufficiently.
However, the mike will be a moving coil dynamic type and its output will be insufficient as a workable input to the PC.
The PC mic inputs are meant for "condensor" mics, and they have a DC feed (5 Volts) thru' a 4.7K resistor.
I'd suggest using a pair of ampli speakers and a PC mike. Unless, of course, you don't want to use speakers.
Ramesh