Hi there,
Unfortunately, trying to make an accurate estimate from the information you've provided is rather difficult since your SAC marks are going to be moderated based on your exam performance and your class's performance overall. There is some more technical stuff about the distribution of scores in internal assessments but I don't think you would have that information, so I won't go into it.
However, if we make a few assumptions, it is possible to make one just from your exam score. One of those assumptions is that overall performance of your class hasn't drastically changed throughout the year. Steady improvement is to be expected, but as long as you don't have a case of scoring 60% and then 90%, it should be fine. The other assumption is that the difficulty of the exam compared to last year is marginally the same. (This is the important one).
We can use the below graphic to help.
According to the 2017 data, one could expect a raw \(39\pm 1.5\).