Figure 5,500 lb with the loader and boxblade as a minimum. 6,000 lb would be a safer bet. A tandem axle utility trailer with two 3,500 lb axles will be overloaded by about 500 lb. You really need a 10,000 GVWR trailer to haul your tractor. A 14,000 GVWR would be even better and allow you to add other weight.
I also would not haul that tractor with anything less than a 3/4 ton pickup and brakes on at least one axle. I tried to haul my tractor (a TC45D with loader) without loaded rear tires on my 18' 7k lb utility trailer without brakes. Even though my pickup is a 3/4 ton, a light rain put a slick glaze down on the highway. I went sliding through an intersection at a stoplight. Luckily, nobody else was in the intersection. I turned around and went home. Never have I hauled my tractor on that trailer since then. It ain't worth it.