I can not say for sure, but I think a tandem axle trailer about 18-20 foot ling would so the trick. Make sure the trailer has at least 3500 pound axles. Make sure you are pulling your trailer with at least a 3/4 ton pick up. If you meet these minimum requirements I think you will be ok. I think you will be pleased with you truck-trailer- tractor rig/set up.
Angriffnole: Agree with PhillipW in most respects. You are going to have a 4000lb tractor and whether the loader weighs 1000 or 1500 or 900 isn;t going to make all that much difference. To be on the comfortable side, especially since you have not yet BOUGHT the trailer, as Phillip said get one with a GVWR of at least 7000 lbs. That means the load plus the trailer minus the tongue weight would not exceed 7000 lbs. If I were doing it, I'd recommend using 5200lb axles with 6 lug wheels. Very common and not much more $ than the lighter ones. That way you are comfy in all respects regarding capacity including later on deciding to throw on some other implements.
That leaves type, size and brakes. If you're reasonably sure you won't be hauling more stuff stacked on there besides the tractor and loader then 16' is long enough. Use your own contingency ideas to figure if you want a longer one. Are you hauling long trips and sometimes mountains -- or -- just farm to farm to shop ? If the latter you won't really need brakes. If the former, add brakes to at least one axle.
Type: If you get a "utility" trailer tandem axle 16 or 18 ft without brakes (kind with rail around the top above the bed) you can expect to pay around $2000. Many sources. If you get an"equipment trailer" meaning it has a flat bed with no rails around the top, does have brakes, room for stuff to stick out over the sides, etc. 18 or 20 ft. you can get it for around $3000, many sources. While you are at it, look carefully at WIDTH. Utility trailers with side rails will often not accommodate things like belly mowers, bush hogs, etc. unless you get the "extra wide" models.
OK, final comment-- where I do disagree with Phillip -- you do not need a "3/4 ton pickup, " much less anything bigger. I have used an F-250 V-10 pulling a heavy 3000lb+ Pequea trailer with 10,000 lb tractor. Have also used an F-150 later model V6 ecoboost. All 4wd. Believe it or not both trucks had the same torque figures. The aluminum F-150 is marginally light, the F-250 was plenty heavy. In your case with a lighter trailer and
much lighter tractor the "half-ton" F-150 (or equal in some other brand) is all you need. For sure use 4WD if possible since a 2wd pickup is like a 2wd tractor. Stuck somewhere. Secondly, the 4WD usually has a low-speed choice on the trans and better load capacity whether half ton or 3/4 ton.
Sorry for the long winded version. Good luck with your purchases !