First time user wanting to setup internet and bridge on Netgear DM200


22.03 introduces Firewall 4 and nftables which does things differently from the Firewall3 and iptables base of earlier versions which is why you couldn't find that item.

I'd recommend that you start a new thread specifically for running Pi-hole in conjunction with Firewall4 and nftables to tease out what needs to be done to implement a replacement for the functionality in that step of your reddit guide.