Evangeline
You can import your PSE3 catalog into Lightroom, if you had a PSE3 catalog.
By the way, whoever told you that PSE3 could not handle a catalog of 54''' images was wrong, and probably just trying to sell you a more expensive piece of software. Catalogs of over 5'K images have been reported running well under PSE. Adobe often tells people that PSE can't handle more than 1'K, and that is quite simply baloney.
Nevertheless, you may be able to export your tags and captions and GPS locations to your files from PSE, and then import the files that now contain tags (Lightroom calls them keywords), captions and GPS Locations into Lightroom, and Lightroom will recognize this metadata. You would lose your PSE collections/albums, version sets and stacks. To do this, in PSE7, select all of your files, and then select File > Write Keyword Tag And Properties Info To Photo. NOTE: this does not work with some types of RAW files and also has been known to fail without warning in rare occasions for .jpg files.