Office 2012 - needs to upgrade?

Forgot to answer:

The only choice is Office 365.

I don't have any problems as such - but will I have to pay???

All it says is 'Get App' in the App store. On the left in grey almost unoticeable writing it says 'In App Purchases' or something.

Yes, for Office 365 you would have to pay. In the App Store you pay through Apple. With Microsoft you have the option of either Office 365 (subscription) or a standalone purchase.

There isn't (wasn't) an Office for Mac 2012. It was Office for Mac 2011 and then Office for Mac 2016.

If you have an early version of Office for Mac 2016, you can update it at no charge. See: https://docs.microsoft.com/en-us/office365/troubleshoot/administration/office-2016-for-mac-64-bit-upgrade

If you have Office for Mac 2011 or earlier, Microsoft does not offer a free upgrade. You can either subscribe to Office 365 or you can make a one-time purchase. Personally, I would do that directly with Microsoft rather than through the App Store. See: https://products.office.com/en-us/buy/compare-microsoft-office-products-for-mac?ms.officeurl=mac-compare-redir

Or do one of the following free options:

The free Microsoft Office on the web: https://products.office.com/en-us/free-office-online-for-the-web

Or Google Docs: https://www.google.com/docs/about/

Or the free and very good Libre Office https://www.libreoffice.org/

or Apple's Pages and Numbers