I believe you mean "Nikonians"... as in https://www.nikonians.org/

There have been a number of good suggestions I agree with:

KEH.com, MPB.com, B&H Photo Used Dept., Adorama Used Dept., UsedPhotoPro.com (Robert's Photo) and some other reliable retailers buy used gear to stock their shelves. While it will vary a bit from one to the next, in general they will pay you a fair, used WHOLESALE price for your gear. It's probably the easiest way and lowest risk way to sell your gear, but will get you the least $ out of them.

Selling via an on eBay (and similar) can produce a better $ return, but there's no guarantee and there's some risk with shipping, dishonest buyers and some $ end up going to auction fees, shipping, insurance.

Selling on a forum like UHH or Nikonians also can produce better $ return than wholesale and typically has a lot less risk than auction sales. You can check a member's history... how long they have been a member, if they have had other transactions, etc. There still will be cost of shipping and insurance, but you can negotiate that if you wish.

Selling locally via Craigslist and similar is also possible and can make for better $ return than wholesale, but you do need to be careful. Meet the buyer in a bank lobby, inside a coffee shop, or similar... for your own safety. Be prepared for some haggling over price. People love to play games. For example....

I sold a motorcycle via Craigslist. We had agreed on a price over the phone and when I counted the money the buyer handed me, it was $20 short. He said, "Whoops, I thought I counted that right. It's all I have." Yeah, right. And neither of the two friends who came with you have $20 they could loan you either, right? I knew it was all BS, but do I kill the deal over $20 or accept a little less than we had agreed? Obviously $20 wasn't all that much and letting the deal go through made him feel like he'd "won".

higgs I would suggest you start here

Members Buy/Sell/Trade -- Classifieds
https://www.uglyhedgehog.com/s-6-1.html

That said please review the Admin's Rules on this forum carefully first.
Also I would invest some quality time reviewing other UHH members posts in the forum.

If you don't feel like investing time coming up the curve selling here on UHH then I would suggest
KEH; mpb; B&H; Roberts; UsedPhotoPro; (btw, Google is your friend here)

eBay is another option albeit it also requires that you invest time/effort to get your head around how that marketplace works.

My question to you is Why are you asking here on UHH since you joined in Sept 2019 and have less than a half dozen post?

Maybe Craig's List in your Locale is what you should try in my humble estimation since seem to lack any serious commitment to UHH and it's members. UHH is a family of Photographers where synergy with other members is an important attribute (hope this makes sense)

All the best on your Sales/Marketing venture higgs.