How do I find the value of ##log 1000##?

The answer is 3.
You can do this in 2 different ways.
One is to just plug it in your calculator, and the other is by hand.
By hand, you need to know that ##log## is the same thing as ##log_10##.
Therefore, if you rewrite the problem as such, you get:
##log_10 1000## = ?
From here, it would be a lot easier to solve this problem by converting the logarithm into exponential form (which is simply something with an exponent, like ##5^2##)
To understand how to do this, refer to the image below:
So therefore we can rewrite the problem as:
##10^? = 1000##
And if you know your exponents right, you’ll know that ##10^3=1000##
Hence, the answer is 3.
To know more about how logarithms work, please refer to my explanation in this I contributed to.
Hope that helps 🙂