At least 4.5 miles per hour.
3.281 feet per second (about 2.24 miles per hour).
You can walk fo about 2 miles
one meter = 39.3700787 inches
You'd have to walk 500 miles, then walk 500 more.
3.8 miles = 611550.72 cm.
You will walk 8.04672 km
about 532.5 miles
2.5k is 1.5 miles
3.2 miles
3.10686 miles.
It is safe to walk any number of miles. Limited only by your stamina.