Help! Can you advise how to remove this 4" round steel lid?

[Scootch]

The attached pictures represent a 4 inch round steel lid of sorts, on the end of a steel pipe. This was from a shower, and what the shower drain drained into from the P-trap. I'm a novice, but is there a way to screw this off, any particular or specific tool I must use? Or, is this a "gotta call a plumber"? I am super and incredibly appreciative of any help, advice, thoughts, or insight, thank you!

 

[Geofd]

Just cut that broken part of the pipe flush with the hub, home depot/Lowes makes something that pushes into the pipe with a wing nut to tighten it, expanding the fitting I call it a spin tight can't tell if it's cast iron or galvi but you can cut both with a saw all or grinder

 

[Scootch]

Just cut that broken part of the pipe flush with the hub, home depot/Lowes makes something that pushes into the pipe with a wing nut to tighten it, expanding the fitting I call it a spin tight can't tell if it's cast iron or galvi but you can cut both with a saw all or grinder

THANKS! Anyone know what this Home Depot/Lowes item is called?

 

[sawguy]

THANKS! Anyone know what this Home Depot/Lowes item is called?

Test plug.