According to the Arduino pin Mapping
20 PB12 SDA 3 6
21 PB13 SCL 3 6
70 PA17 SDA1 3 6
71 PA18 SCL2 15 9
The first one seems pretty obvious, the second one though is confusing. They have different labels. I also do not see other SDA or SCL in the table. So is this a typo?