convert the font of endnotes from a particular font to the expert font in an easy way

You aren't going to like much of anything you hear. 😞

InDesign is an intensely style-driven app; while you can just dump text in and spot-format it, as most Word users do, that approach quickly becomes an unmanageable mess of expanding size. Many a new user has "finished" a book or other document in this manner only to find the downstream problems and issues are somewhere between monumental and unsolvable.

For a book of a scale to have 700 end notes... there is almost certainly no "fix" for any problem you're likely to encounter at this stage, simply from sheer scale of what it would take to apply those fixes.

With more specific questions and discussions, you might get guidance to fixes for what you see as the book's problems, but it will still have others built into the structure, and simple things like changing the page size (to suit a printer, for example) or generating an index could be nearly impossible.

So: the real answer here is to start more or less from scratch and set up and refomat your book using the basic accepted principles of how InDesign works best, which means (basically) that every single element in it — every paragraph, every local text style, every repeating object like included graphics and tables and the like — has a defined, named style assigned to it.

You may want to start with a few of the basic tutorials on how to do these basic operations. There are a number of them, some here on Adobe, others on resources like Lynda and LinkedIn. It's not extremely complex, but it's not something that can be taught a few sentences at a time in a forum. You need that basic 'grounding' in a slate of fundamentals for the practices, and further information, to make much sense.

If you had structured your book correctly, your problem would be simple to fix: you would just make slight adjustments to the style assigned to your end notes (say, "End Note Text") — and each tweak of font, size, spacing etc. would instantly apply to every one of those 700 notes. That's how, and why, styles are the fundamental element in professional page design.

I've moved your discussion to the InDesign forum!

I've asked and nothing happend, so I suggest you might try starting a new discusson in the InDesign forum.

This question isn't really about a font, but about your app. But... What app are you using? If it's InDesign or FrameMaker you'd just change the paragraph style.