Howdy & Welcome DS . I,m not Familiar with that model Either , But by looking at the replacement Piece I would say You,ll have to drill a small hole in the center where its broke off flush & use an easy out to get the rest of the broken piece & threads out .
But If its Where I think its Located it could leak fluid or gearoil out when You get the Broken piece out , So I,d have a drain pan handy . Once again its just a guess not knowing the tractor . Best of luck . Bob
After looking at it again , It Might be more helpfull if You can take a pic of Where it broke off of the Tractor . Are both sides Exposed where You can see them Or is it posable You have to get into the rear gear box to Remove the other piece & replace it . Sorry I,m not much help .