Lexile / Accelerated Reader Comparison Chart
You can search the Mission Library catalog for books by Lexile level, but most books do not have leveling information in the catalog.
You can check a book's Lexile level online by doing a Quick Book Search from this website.
You can check a book's AR level from this website.
Mrs. Bloom has also created a Google Spreadsheet listing selected high reading fiction level books on one tab, and selected Open eBooks by reading level on the other tab.