My dad just gave me an old Winchester 94 44mag Trapper.  Where do I send it to get it threaded?

Threaded? That would be an abomination...

I think I remember someone. See if I can find the contact information.

Why in hell would you.................?

Send it to Morgan at Class 3 Machining. @eastTXhunter

Make sure it feeds reliably before spending any money.  The 94 mostly doesn't like pistol cartridges.

First, you need to determine it's current value.

An 'I have this old gun' article snip taken from a 2016 American Rifleman:

"...Original trappers with barrels less than 16" must be declared a Curio & Relic by the Firearms Technology Branch of the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF). However, ATF authentication is not required for the Model 94 trapper shown here, which has a 16" “Special Carbine Barrel” described by the late George Madis in his classic, The Winchester Book. Unfortunately, the magazine tube has been replaced, the wood has been lightly sanded and the front sight is bent. Additionally, the receiver and rear barrel band have been polished, probably to remove flaked bluing on the nickel steel, although traces of original bluing remain and the bore is sharp. Were it not for the magazine tube and receiver issues, it could have fetched $6,000 to $8,000. Even so, this trapper would easily bring $2,850 to $3,500 at a gun show. "

I guess I should not have put "old" in the thread title.  This is a crossbolt safety gun that is probably 25 to 30 years old.  It has some light surface rust as it has lived in a case behind a bench seat in a farm truck most of its life.

I focused on "old" and in so doing completely missed the ".44mag" part.

Morgan at Class 3 has done several lever guns for me though none were Winchesters.