I'm not sure if your already aware but when you upgrade your 2016 Explorer from MFT to SYNC3 you don't gain any extra connectivity to the vehicle. Yes, FordPass will show your vehicle but there is no remote start, no fuel level, no tire pressures, no vehicle diagnostics if that was your purpose.
Yes SYNC3 is an improvement over MFT because of how poorly executed MFT was but please be clear on what you will gain.
Perhaps someone here who has completed that upgrade can comment.
The SYNC3 system didn't allow FordPass Smartphone connectivity until 2018 when they added the 4G modem.
I use 4G FordPass connectivity at work on a 2018 F150, its just OK.
The 4G data packages Ford offers in comparison to On* are too expensive so customer use is minimal.
You might be confusing the other In-Vehicle Connectivity System that Ford introduced for older vehicles like your 2016. This system was called SmartLink and yes, as Jason stated, it's being discontinued.