You have the symbols right. The numbers after them are the future contract month and year. The symbols are also on the instrument headers in the Pro Scanners. Look for the Rollover notices when you see a symbol that has the current month and year. It will come up when you start Ninja Trader or login to one of the Pro Scanners. They will look like this:
Don’t change anything on the instrument defaults (i.e within NinjaTrader’s Instrument manager) except for the Session Template, as you mentioned, to Default 24/7.
If you look on Apex’s Nadex Scanner Pro and select any instrument and it list the Ninja Symbol at the top of every list of contracts for any specific instrument you have chosen.
Note your months have rolled over Indices are now on March ie ES 03-16