Alright, let’s think about this logically.
When rounding to the nearest thousand, we are looking for the thousand that is closest to the number given.
In the case if 9,138, there is one type of thousand that is best suited for it.
Here is what I do: get two best choices: in this case it would be 9,000 and 10,000.
Now which one is 9,138 closest too?
The answer to your problem is 9,000.
Hope this helped! Comment if you have questions!