Unfortunately, I would say to know them. It doesn't take too long to memorize, and it might save you some time on the exam.
However, on my exam, I had maybe 3 or 4 conversion problems and on every one, the conversion was given for you. Such as grams to pounds. The gave you the conversion right there.
They also had a temperature conversion and gave you the equation for celsius to fahrenheit right there. I was surprised to see that, and spent a while making sure I had that one memorized.