Well, first you would convert 1 hour into seconds which is 3600 secs.
to find how far it travels in 3600 seconds, do 3000ft * 3600sec which is 10,800,000ft.
you convert that into miles and you get the answer.
1 mile = 5280ft.
10,800,000ft / 5280 = 2045.45miles
Therefore the mission goes 2045.45 miles in 1 hour or 2045.45/mph
hope this helps