I know they're Makkah, Medina, and Jerusalem.
Makkah is important to Muslims because there, they have the most sacred symbol which is called Ka'abah
And Medina is important because it is where the prophet Muhammad lived, and it is where islam started to spread
Jerusalem is important because it is believed that the prophet Muhammad ascended to the heavens from there, and also it is important for them because it is connected to Abraham, Moses, Jesus and other prophets.
Hope that helped!!