Drain help for new acrylic shower install

Hi! I've just removed my old leaking tile shower and want to replace it with an acrylic shower unit. Can anyone tell me what type of drain I have left here, and what to remove/how to connect a drain for an acrylic unit to it? I'm on a concrete slab, and I think this drain is cast iron, as the house is about 30 years old. Thanks, Amoreena

drain

It is hard to tell with the mortar still attached to the drain fitting, but it appears to be a cast iron unit. That has little relationship to the type of pipe, however. It is either screwed onto the riser pipe, or attached to it with a lead, or rubber joint. We cannot tell which of the above applies to you or the best way to remove it since each type of pipe and attachment requires a different method.