I see several builds of Movie Studio 12 Platinum Edition, but i don't know if that's the one you had.
Do you have a serial number? You'll need it in order to activate the software.
Did you register the version you had? If so you would be able to find a direct download link and your serial number by going to My Account / My Software from the menu at the top of this page.
With only one single exception many years ago when they issued a "patch", all Sony Creative Software "updates" are the entire install package. Any one of them on it's own will install the software successfully.