# import necessary libraries
import pandas as pd

# Create a series of numbers
s = pd.Series([1, 2, 3, 4, 5, 6, 7, 8, 9, 10])

# apply where() method with a lambda function
new_series = s.where(lambda x: x % 3 == 0)

# drop NaN values and get index 
positions = new_series.dropna().index

# convert into series and print
result = pd.Series(positions)
print(f"Positions of Multiples of 3: \n{result}")