I've updated the sync3 software in my 2017 UK Focus. Here are some notes that may help if you are in a similar situation. This is for UK versions and not for other countries where the update process is different.
The latest Sync 3 in the UK seems to be Version 3 and it appears there are no map updates for the Sat Nav since 2014/15.
To see if there is an update put you VIN number in
You need a USB stick formatted as exFAT OR Fat32 (the update files are less than 3G bytes).
Download the update files from the UK ford web site listed above and decompress them (unzip them)
Transfer the files to the USB drive and you should end up in the top level of the drive: DONTINDX.MSA autoinstall.1st SyncMyRide (folder)
This latter folder will contain 8 off compressed files xxxxxxxxxx.tar.gz. The software in the car will decompress these files.
Follow the instructions BUT NOTE that it may take 10 minutes for the display in the car to actually acknowledge the USB stick and indicate that the update is taking place. DON'T ASSUME THAT ANYTHING IS WRONG with the USB stick, formatting or files until at least 10 minutes has elapsed. This is different to what normally happens when you plug in, say, a USB sick with MP3 music files and the car acknowledges the stick within seconds.
Part way through the update the sync3 with reboot. Again it may not acknowledge that it is continuing with the update for more than 5 minutes after this reboot so don't panic if you think something has stalled.
In my case the install required no user intervention from plugging in the USB stick to the update reporting finished.
The car will write a file back to the USB stick in the SyncMyRide folder Sync_yyyyyyyyyyyyyyyyyyyyyy.xml If you now go back to the web page where you entered the VIN number for the download you should see a button "confirm your update" and on clicking this it will ask for this .xml that the car wrote back to the USB stick.
I updated to try and get a Sync 3 compatible app on my Andriod phone to appear on the car's screen. It only partially worked but the problem is probably down to an old version of Andriod installed on my 4 year old phone