First you will need to find three definitions of philosophy, two from philosophical books (but not textbooks), and one from a philosophical reference book. You will need all three of the definitions (you can condense and paraphrase them), citations for each, and the sources for them.
To find academic books containing a definition of Philosophy, try searching the library book catalog below. Two effective searches are introductions and philosophy or philosophy and history . Many of the titles in the results list will provide definitions and an overview in the introduction or first chapter of the book.