+1, [simplifying the how to stuff I wrote earlier] just Get a threaded headset, dude .

if you then want to use a threadless stem, then buy a conversion plug ,
7/8" quill on the bottom, with a 9/8" diameter on the top to grip with the stem,
of your choosing

the carbon fork is questionable, used, you don't know its former life..
could be hidden surprises.