[dejacky]

Does anyone know how I get this threaded piece out of my old suspension fork so I can re-use it in the new stem of my new fork?:

 

[Sghost]

hammer and pipe or buy a new one

 

[JustMtnB44]

Star nuts are not really meant to be reusable, but you can pound it all the way through the fork to get it out. My advice is leave it there and buy a new one (they are $5 or less) for the new fork. If you buy it at an LBS they can install it for you too since it can be tricky to get it straight.