I'll add something to juancarlospaco's helpful explanation:
var
k: array[10, int]
for i in k.low .. k.high:
k[i] = (i + 1) * 10
if k[i] mod 2 == 0:
echo k[i]
RunNote the `.low` and `.high` in the loop. That's a good way to avoid index errors and also allows you to later change your array to, say, start at 1 instead of 0 and the loop will still work fine.
