You would have to re-install it from the iLife DVD if that was where it was from, unless
you had an older version that was included with the Mac and its original DVD install kit.
{Given your info says the computer is running Snow Leopard 10.6.8, that's not likely to
be one of the versions available as download purchase for later OS X via App Store.}
Replacement (second-hand or new-old-stock) iLife DVD versions including iPhoto,
iMovie, and others, vary depending on the version number, and may be found online
at resellers such as Amazon, ebay, or perhaps some Apple centric resellers online.
•iLife: System requirements - Apple Support
System requirements for older versions of iLife
Anyway, hopefully you have an original install DVD for iLife, if not something similar
to the version you had installed. A backup (with an additional clone-copy on external
hard disk drive, etc) is always a good idea; not just a Time Machine setup.
Good luck & happy computing! 🙂
edited 2x