.
...if you don't want to do this ^^^ (or cannot find a place to do it for you), if there is enough unthreaded length on the steerer remaining after you cut off the threaded part with a hacksaw, youi can find yourself a 1" threadless headset, and just go threadless. But you have to buy a new headset, and stem, and it looks very different. Plus 1" threadless headsets are difficult to find (but not impossible), as are 1" threadless stems (but you can use a shim and a 1 1/8" stem...those are more plentiful.)

Possibly your best option (once you find a headset that works with your fork), since you want some extra steerer tube length, is to use a bunch of 1" spacers under the locking top nut of your selected headset. They are readily available online. It looks kinda strange if you go to far in that direction, but it keeps your headset adjusted and youi can use the same stem you have.

Not certain why you decided to go with front suspension. If it is because you are gonna ride the hell out of this bike, a longer steerer length and spacers is probably a less good idea.