"I didnt see how to do disable it when going to the modems website config page"
Don't highjack someone's thread with your own concerns - if you want to do something with your "gateway" then create your own thread. As .fahim has clearly pointed out, we don't have clue one to what the OP is wanting to do. Guessing that they want to put their gateway into bridge mode is just that, a guess.
I think he wants to setup a wireless bridge/client and connect to his gateway using this other wireless router
I really think we need to get some terms pinned here in this thread.. You don't put a "modem" into bridge mode
If it was a "modem" then it wouldn't be doing NAT in the first place
With the way terms or interchanged its quite often impossible to know what the user has without a model number given. They say they have "modems" when really what they have is a gateway and are behind a NAT, etc. They have 2 devices connected together with the first one being a gateway and then a 2nd router so they end up being behind a double NAT, etc..
modem - connect you to your ISP, does nothing but make the connection quite often changing media - be it phone like to ethernet, or cable RG type connection to ethernet, Fiber to ethernet, etc. Does NOT do NAT, your device connected to this gets a public IP. If it gets a private then your behind a carrier nat, etc.
router - does just that routes and nats, quite often wireless is provided as well, bridged to the lan ports. Ethernet as input - ethernet as output.
gateway - combination of the modem and router. Now a gateway is the type of device that you can put into "bridge" mode - disable its nat, etc. If your connecting with some sort of DSL or ADSL technology most like you have this. And is becoming more common in the cable connection method as well. But at least in the past if your internet was "cable" based then you normally got jut a plain jane modem. And you need a router to do the NAT for you and if so desired add wireless, etc.