When you download a new studio pro version you can open the same project in the newer version. The app will then ask ‘convert to newer version?’. you then press yes and the update will be handled by Mendix studio Pro.
If you are moving from major version (Mx 8.X.X → 9.X.X) you can find more information here:
Be aware, some newer versions cannot be converted back to the previous version. So make sure you read the documentation!