I did my research and found out in order to get my TT685 flashes to
work with my trigger I had to not only set the channel and group but
also set them on an "ID" located in the menus.
Actually, you don't need to set the C.Fn ID to anything; it just has to match on all your units. You can have this feature set to OFF on your transmitter/lights if one of your lights (say, a TT600) cannot use it. The ID feature is only to stop someone else in the same vicinity with Godox gear on the same channel from triggering your lights. It's not a required setting like channel or group.
... Here is my problem. I went now to my Godox AD200 and there is no menu
where I can change the "ID"
Check the firmware version on your AD200. The ID feature was only introduced with the arrival of the XPro transmitter unit into the Godox system. The AD200 was released before that, so, if you purchased it used or have owned it for a long time, it may not have been firmware-updated to include that feature.
On the AD200, firmware v2.1 added the C.Fn ID to its menus.