It’s the same basic download for both Free and Pro versions.
It downloads as Free and then needs to be activated as Pro.
Depending on just where/how you downloaded it that can happen automatically - but if it doesn’t then you can always do it manually:-
Install CCleaner7 as Free.
You can get the latest installer here if you need one: Download CCleaner builds | CCleaner Portable, Slim, and more
Open it and go to Settings (the cogwheel) > My Subscription.
Enter a valid licence key to activate it as Pro.
Job done.
PS. If it’s already activated as Pro then that 'My Subscription" page will show the licence key and when the current subscription expires.
See this for more details and screenshots: