Word for converting grades from one system to another?

Solution 1:

The process of taking grades from one grading scale and changing them to match another grading scale is commonly called grade conversion.

Saying you're going to convert your grades is fine and easily understood. Trying to find a more specific word might actually make it harder to understand what you mean.

I almost have everything ready for my university application, I just need to convert my grades.

If you want to be more specific you can say

...I just need to convert my high school grades to the scale used by X_University.

This is actually something that happens not just from one country to another but even within a single country for different schools. In the US there are many different grading systems in use, and converting grades from one system to those of another is a common requirement. Many schools provide formulas charts or spreadsheets to help with this, and there are online tools like this one specifically for converting between grading systems in different countries.