What type of word processing program is available for an IPad Pro?

You can either use Apple Pages, pay/subscribe to Microsoft 365 apps, like Microsoft word.

Other third party apps, like other subscription apps called Ulysses, Bear or Werdsmith.

There's Textilus Pro.

Scrivener

iA Writer

Mellel

Good Luck!

Several, Pages is the Apple program. That would be a good place to start.