The Ford Body Builder (Publications) Web site (link here
) has useful information for your 2015 E-Series chassis. In particular, the 2015 BBLB ELECTRICAL WIRING document (link here
), page 14, shows the location and pinout of the trailer electric brake controller connector. The entire document, up to page 24, is worth your review (in my opinion).
The Tekonsha P3 controller is a popular recommendation. You may be able to install a Ford brake controller. I have no experience with doing that; it may require a trip to a Ford dealer to properly integrate the controller into the truck's CANBUS network.
As "A32Deuce" said, you can get a pigtail to make a Tekonsha controller install plug-and-play. Here is a link
to that pigtail on etailer.