To retrieve the IP address from NetSuite you navigate to Setup > ZoneReconcile Setup > Connectivity SFTP (in older versions the path was Setup > SFTP Connector > Connection Configuration). If you already have a connection configured you can simply open one of the configurations and the connection configuration will show you the current IP address from your NetSuite system.
If you do not yet have a connection configuration then you can create one with basic information. To create a new configuration press the blue button labeled New Connection Setup (in older versions known as “New SftpCon Connection Configuration”). On the screen that opens enter a name and then press save. After saving the page the NetSuite IP address will be visible.
Disclaimer
The IP address from your NetSuite account is not a static IP address and is subjected to change. It is recommended to Setup IP Change Reminder.