You can't download those programs to your iPad. The only way to get software on the iPad (aka "applications" or apps) is to download them from the App Store. However, Word and Excel are not available in the App Store for downloading.
There are many, many apps that can view, and do editing of, Word and Excel files. Many members here have had success with Numbers (Apple's spreadsheet app), Pages (Apples's word processing app) and Documents To Go and Office2 HD, both of which are general purpose office apps. Again, there are many, many apps in the App Store for using Microsoft documents.
All I can suggest is to look through the description of the apps I've mentioned to see if any will suit your needs. Do note that none of them perfectly emulate Microsoft's native programs, but they do come close.
Hope this helps and clarifies.
Marilyn