Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
Hi Jerri, Just to add to Karl's post. For every day tasks there is not much difference between Office 2013. If you have Office Home and Business 2013, with Outlook. Outlook is much improved with Office 2021. Microsoft has withdrawn support for Office 2013. I would suggest that you leave Office 2013 on the old computer to use as a backup and purchase Office Home and Student/Business 2021.
Most of Office Professional 2021s on this forum are Pro Plus versions purchased on the internet at knockdown prices in contravention of the Microsoft licence. Nobody seems to care, not even Microsoft Agents, who assist users. Some have Office Accounts, some work for a long time, some for a short time and some don't work at all. They cost in the region of $30/40 or £30/40. Anything less will almost certainly be a bad deal.