He pasado un catálogo de fotos de Photosoph Elements a Ligthroom Classic y no se como localizar las

"don't know how to locate the photos by the names of the tags they already have."

If I understand the question correctly- And hopefully the keywords were imported from the Photoshop Elements catalog!-

1)

Open the Keyword list panel

Click on the white arrow that appears when you hover the cursor on a keyword (tag)

2)

Or- Use the Text Search Filter for Keywords. (If the filter line is not visible. press [ \ ]

3)

Or- Use a Metadata Filter Search with one of the column headers set to 'Keyword'