Q: how do i download past purchase that i purchased (it only show the last ten) how do i download all?

What you can redownload will depend upon what country that you are in (music, films and/or TV programmes can't be redownloaded in all countries ; audiobooks and ringtones are one-time only downloads), and if they are still in your country's store.

On your iPad what you can redownload will show in the Purchased tabs in the iTunes and App Store apps, and in the Purchases tab in the ibookstore in the iBooks app. On your computer's iTunes it will show under the Purchased link under Quicklinks on the right-hand side of the iTunes store homepage (that should also give you a 'download all' option for the content type at the bottom right of the screen).