Kevin needs to convert 620 millimeters per minute to meters per hour. which conversion factors should he use?

Try this option:
1 meter=1000 mm; 1 hour=60 min. From another side: 1 mm=0.001 m. and 1 min=1/60 h.
Using this rule:
620 mm/h=0.06*620 m/h=37.2 meters per hour.

0.06