How to rebuild the Spotlight Index.:

Choose System Clean > Rebuild Spotlight Index.
IIn order to let you find files quickly on your Mac, Spotlight keeps an index (database) of files. When Spotlight can’t find a file that you know exists, try rebuilding the Spotlight Index.
Choose System Clean > Rebuild Spotlight Index.
Shortly after you run this task the Spotlight magnifying glass at the top right should start animating to indicate that the index is being rebuilt.