The following instructions were taken in part from https://kb.netgear.com/30773/How-to-set-DM200-into-bridge-modem-only-mode
Connect directly to your Netgear DM200 (connect an Ethernet cable from the LAN port of the DM200 to your computer).
Connect to modem on 192.168.5.1 in a web browser.
Default Username : admin
Default Password : password
First check the firmware on the top right hand corner is at least v18.104.22.168. If it is then you can skip the firmware upgrade.
Download and follow the instructions from NetGear the latest firmware for the DM200. This guide used Firmware Version 22.214.171.124
Click on Advanced > Administration > Firmware Upgrade
Click Browse and “Locate and select the upgrade file on your hard disk. The click “Upload”
After reboot we need to setup as modem only with Passthrough VLAN.
Configuring Modem for Bridge Mode
Device even though you click Passthrough VLAN mode it will default to off.
When you click apply the modem will reboot and you will loose access to it. The only way to access is to manually set a static IP address on your computer i.e 192.168.5.2. The modem should now work with VDSL mode. You can now connect your router to the modem.