Probability is an integral part of Finance in general. Specifically you really need to know and be able to interpret the normal distribution and how that relates to quantifying risk. Be very comfortable with covariance, correlation, confidence intervals, and expected value.
The graphical side of the readings as well (histograms, distributions, cumulative distributions and so on) always get tested on a few questions and are hopefully easier to grasp.
More specific topics like conditional/unconditional probability, the joint probability rule, Bayes formula, and counting rules could all be tested, but will be more generally confined to the Quantitative methods section of the exam. If you work backwards from the overall weighting those will probably be worth comparatively fewer points than concepts that spread throughout other parts of the curriculum as well.
Above all try not to get bogged down in Quantitative methods. You can always hammer practice problems and come back to it later, but don’t let it derail you from pushing forward aggressively to the rest of the material.