Two things:
1. You may not actually need Microsoft Office at all. There are plenty of substitutes -- most of them work rather differently, but they are all highly capable and compatible with MS Office. There's Apple's own Pages software (roughly like Word), Numbers (barely like Excel, but covers the same basic concepts), and Keynote (superior to PowerPoint in my opinion). There's the free LibreOffice or OpenOffice. There are individual word processors and alternative spreadsheet programs and alternative presentation programs (Mariner Write, Mariner Calc, and Fotomagico, respectively, among others).
2. Office 2016 is highly recommended if you must use Office, as its the best version the company has put out in at least a decade. It can be purchased as a standalone or as a "subscription" model (which works out considerably cheaper, particularly if you also take advantage of the free cloud storage). As Charlie notes it is possible to run an older version of MS Office on your Mac, but it will simply go obsolete/non-functional more quickly.