What is the courses file type sent to my Edge 530?

You can look in the file system on the Edge to see the course files.

Courses are saved as FIT files.

Besides saving the activity as Course, you can also export the activity directly in FIT, TCX, GPX, and in KLM formats from Garmin Connect Web, in case you need a specific file format. Similarly, Courses can be also exported from GC Web in two different file formats - FIT and GPX.

Thank you.  I hadn't thought  of that.

Now I see that.  Do you know if the TCX is a TCX Course or TCX History formatted file?  Per, RWGPS:

TCX Course: contains turn by turn navigation data for use with Garmin Edge series GPS, Wahoo ELEMNT, Hammerhead Karoo and other compatible devices.

TCX History: contains ride history, like speed data, date and time, duration, and more. These files do not provide turn by turn navigation.

For the Turn-by-turn navigation, you have to save the activity as Course, and then export from the Courses page, after having enabled the Turn Notifications.

I cannot find the "Turn Notifications" dialog box?  It seems it is only for wearables, not bike computeres like the Edge series. 

Garmin support says Edge 530 turn by turn guidance is enabled on the device under the Course Options menu item onboard the Edge.  They also pointed me here:

 https://www8.garmin.com/manuals/webhelp/edge530/EN-US/GUID-5FB6AF7B-6157-4AFC-B82B-C3AEED568646.html

 Do you know for a fact that this is wrong for the Edge?

bikeskiii said:

Do you know for a fact that this is wrong for the Edge?

I do not own Edge 830, but my understanding is so that you can enable or disable the turn prompts on the device, though with the assumption that the turn information is included in the course file.

BTW, if you just want to send the Course to the device, you do not need to bother about the format, or download the files. Just enable the turn prompts in Garmin Connect, and then hit the button "Send to Device". No exporting is necessary.