[Forminator Pro] How to replace Forminator Free with Pro to remove branding and ads?

Hello, first I had installed Forminator Free to the site and added some forms. Now I wanted to swtich to Pro version in order to remove the branding and more importantly: the ads at the bottom of the Forminator Dashboard.
So I have activated the white label feature in WPMUDEV-Dashboard, disabled all branding items and went back to Forminator Dashboard, but the adds were still there.
So what now? How to remove those ads?
If I uninstall Forminator Free and reinstall the Pro version, what will happen to the forms and entries?
Thank you and kind regards,
Sascha