Facebook's in-stream ads programme asks for 60,000 minutes viewed in the last 60 days (plus followers and active videos). These packages deliver that watch time on a single long video.
Pick the package that matches your video's length — 1 hour, 2 hours or 3 hours. A longer video needs fewer viewers to reach the same minutes, which is why it's cheaper. Bigger packages (120K, 180K, 600K minutes) are listed for pages scaling up.
Keep the video public and unchanged until delivery completes.