Bought iWork, now using on a Mac Pro. Now need advice for using that on iPad

I'd like to be able to sync Numbers spreadsheet between Mac Pro & iPad. Will I need to buy iPad version on Apple Store? Will the fact that I have a recent purchase of iWork for Mac Pro affect the price for the iPad version. Can/should I get only iPad numbers or the full iWork? ow can I get information about using Apple Store, e. g. can I search for iPad numbers or iPad iWork? Is there a tutorial for using the Apple Store?