Unlike Wonder Woman, Superman and Batman don’t have clearly delineated Golden/Silver Age transition points. However, like JAG2045 said, most fans and comic historians point to the introduction of the Fortress of Solitude in Action Comics #241 (June 1958) as the beginning of Superman’s Silver Age. (In the Golden Age, Superman had a separate, rarely-referenced mountain hideout.)
GA Superman volume 7 seems to run through Action Comics #143 in the early 50s, so factoring in World’s Finest switching from solo stories to team-ups after issue 70 (and thus no longer factoring into page counts for these solo volumes), you’re looking at another maybe 4-5 GA volumes? Just an estimate.