If you have an activated version of SF-9 on an old PC, the serial and user name are stated in the "Help> About Sound Forge" menu. Alternately, your Sony (My Products) serial codes are also listed here, but like Magix, you must log-in using the email address and PW that was used when the product was initially registered. FYI, this info was ported to Magix after the acquisition in 2016. This info also entitles you to receive the upgrade discount to SF-15.
btw, welcome to the Magix Sound Forge users forum @Travis-Townsend,