Typically you would need to copy the \Users\<User>\Music\iTunes folder from your old drive into the \Users\<User>\Music folder of your current drive, then install iTunes. Since you've already installed iTunes you can rename the current iTunes folder in your media folder as say iTunes (Empty) before you copy over the old folder.
It gets a bit more complicated if the library or media were on different paths, but essentially if you copy everything over to a parallel path to where it existed before then it should all work. E.g. if music content was in your Music folder rather than ..\Music\iTunes\iTunes Media\<etc.> then you'll need to copy all of the Music folder over, and either be using the same username/profile folder name, or recreate the old path.
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