I am attempting to setup two Airport Extremes to one Modem.
Whether or not this is even possible will depend on whether you really have a "modem".....or....whether the device that you call a "modem" is really a modem/router or gateway.
A simple "modem" will have only one Ethernet port. A modem/router or gateway, which is actually two products in one.....a modem and a router in a single package.......will have multiple Ethernet ports, usually 3 or 4.
If you are still unsure of what type of product that you have, please post back with the make and model number of the device that you are calling your "modem".
Typically, just daisy chaining airports express works fine
This depends on what you mean by daisy chaining. Are the AirPorts connecting together using wired Ethernet cable connections, or are they connecting together using a wireless connection? Huge difference in performance depending on how things are set up.
I believe I should be able to setup my AP-E as a new router.
Possibly, depending on the type of modem that you have.
Plug in an Ethernet cord to the LAN plug. Turn off the NAT on the second router, mimic the IP address and add a digit in the third group.
If you turn off NAT on the second "router", it won't be a router.
Finally, your post mentions AirPort Extreme(s) in the title, but you mention AirPort Express(es) in your comments along with another device that you call an AP-E.
It would help if you tell us which devices that you actually have. AirPort Extremes? AirPort Expresses? Or, a mix of both products.
What will connect to what in your desired setup? How will they connect? Wired or wireless?
We ask because there is a huge difference in the performance of an AirPort Extreme compared to an AirPort Express, which will determine how you can best set up the network. There is also a significant difference in performance with two AirPort Extremes, if they are different models.
I’m an Noob with Networks
Not if you are talking about NAT and IP addresses, so we're not falling for that Noob stuff.