I bought Sound Forge 16 Pro and got the installers for Izotope RX 8 and Ozone 9 elements, but no serial numbers. I wrote to Izotope support who answered me to write to Magix support but for the life of me, I can't find a way to write an email.
If you cannot find the iZotope serials, email Magix customer service with your purchase info. Though as @SP., stated they are typically in the email message with your SF activation code. infoservice@magix.net