HELP PLEASE... Hitch and extension ?

Both Curt and Draw-tight make 2” 18” extensions, both are rated at 3500# trailer weight and 350# tongue weight…Your’s at 600# is a candidate for troubles…I have one of these:

https://www.amazon.com/Simple-WEIGHTM-Tongue-Weight-Scale/dp/B0B2KLQ62Y/ref=sr_1_4?crid=20EXAPYQPBKMD&keywords=tongue+weight+scale+for+travel+trailers&qid=1691100354&sprefix=Tongue+weight%2Caps%2C171&sr=8-4&ufe=app_do%3Aamzn1.fos.006c50ae-5d4c-4777-9bc0-4513d670b6bc

First thing, do you REALLY need 36" or is that what gets the end of the receiver tube even with the rear of the camper? You usually don't need an extension that reaches to the rear of the camper. It can easily be 12" under the camper. The shank gives you about half of that back, and you will NEVER come close to hitting going forward.

I don't see a "plain old 36 inch extension" for a 2" receiver anymore anyway. Seems like I remember Reese used to make one but the only one I can find now are for 2-1/2" receivers, rated for 6000lbs at 34" extension with a WD hitch.

Doesn't help you a bit because you don't have a 2-1/2" receiver. If you did it would probably work okay, but for the life of me I can't find the 2" extension now.

I’d slap simple tube extension in it and hit the road. But I can’t recommend that officially to you as your inexperience my not allow you to fully understand if something is not quite right.

Go back to the drawing board. Your numbers don’t make a lot sense save for the total trailer weight of 3-3.5k.
1. Virtually any TC with a 2klb dry weight likely won’t need a 3’ extension. Not even if your truck is a short bed.
1a. Or your camper is much heavier if it’s a 9’ model on a short bed or a 10-11’ model on a longbed.
2. 600lbs tongue weight is excessive but probably necessary because you’ll have to back the buggy on that little trailer due to being single axle and the weight of dist of a rear engine rig. You have no adjustability in weight placement effectively. So yeah maybe. But I’d figure out how to lighten up the tongue weight a little.

You’ll have no issues with the truck, hitch receiver or a quality basic extension at 24-30” long. I can’t speak for longer with the same or similar tongue weight.
A weight dist hitch in this scenario seems somewhere between heavy, useless or may not work right. But your truck and hitch will handle it so it’s also not necessary with your little trailer. Interested to see it employed successfully if you do it though.

Update, seems like the tongue weight is going to be around 600LBS