Older version of Numbers software availability

Did you ever purchase iWork apps in the past or get them with a new computer purchase in 2011? You could check your purchases: See your purchase history in the App Store or iTunes Store - Apple Support. I suppose you could also check Updates in App Store, too. Also, see below:

Contacting Apple Customer and Support Service

1. Apple Store Customer Service at 1-800-676-2775 or visit online Help for more information.
2. Primary support help at Contact Support.
3. To contact product and tech support:  Contacting Apple for support and service including international calling numbers.
4. For Mac App Store: Apple - Support - Mac App Store.
5. For iTunes: Apple - Support - iTunes.

Have you tried the App Store?

What is the problem with your Office software? You will find a similar but free suite called Libre Office that you could try.