For the trusted ips box to show up on the multi-factor authentication server settings in 365 multi-factor authentication so you can whitelist IP’s , you need to purchase and activate at least one single Microsoft Azure Multi-Factor Authentication License ( cheaper optoin ) or a single AD Premium License. This will give you the below options

trusted ips (learn more)
Skip multi-factor authentication for requests from federated users on my intranet
Skip multi-factor authentication for requests from following range of IP address subnets