@pycoder64045, you take steps of 3, so we to index 3 and then to index 6, but index 6 doesn’t exist. Index 5 is the highest, which is why 6 isn’t multiplied

We are passing in 3 inputs.
•a list of numbers
•a multiplier value, M
•a value, N

You should multiply every Nth element (do not multiply the 0th element) by M. So, if N is 3, you start with the 3rd element, which is index 2.
If there are less than N elements then you should output the unchanged input list.

Code:
numbers = [1,2,3,4,5,6,]

N = 7
M = 2

N & M can change and do

for i in range(2, len(numbers), N):
numbers[i] *= M
print(numbers)

We get straight to the point when a link to the lesson is provided in the opening post. Help others by not making it so hard for them to know what lesson you are on. Guessing is no comfort.