Answer: 9 ones or 9.
Explanation:
Given statement : "Devin has 39 blocks"
The given number is 39 which is a natural number.
When we look the right most digit i.e. 9 , the place value of 9 is ones.
The digit present just to the left of the right most digit in the given natural number is 3 i.e. the place value of 3 is tens.
Hence, the place value of 9 is 9 ones or 9.