I have an obsolete iMac (mid 2011) running an even older Word and Excel program from 2008. I a lot of important data using this software

dreadznot wrote:

If I upgrade to a brand new iMac will I be able to open my files?

Yes.

Newer Microsoft Office versions usually open older Office documents, and I’ve had success opening older Office documents—documents that Office itself could not open—using the (free) LibreOffice package.

You will need to purchase a newer version of Office with any recent version of macOS. That’s presently Office 2021 (full purchase) or the Office 365 subscription, or (free) LibreOffice, and (free) Apple iWork apps Pages, Numbers, and Keynote can read and write many Office documents.

Make sure you have a complete and current backup of your old Mac prior to upgrade. Worst case, the old environment can usually be reloaded as a guest in an add-on hypervisor, until this gets sorted out.

iMac 27” mid 2011 tops out at macOS 10.13 High Sierra.

If you're not closely wedded to the MS Office apps there are free, open-source apps, LibreOffice and SoftMaker FreeOffice 2018, that can open, edit and save MS Office files as MS Office files or their own format files.

Absolutely. You should know by now that your 2008 Word and Excel will have to be upgraded to work with a new iMac. Your data files, however, will open just. fine.

Microsoft offers two options. One is a subscription to Microsoft 365 which includes Word, Excel, Powerpoint, Outlook, and 1TB of cloud storage that Microsoft has named OneDrive. The second option is a single license, one time purchase of Office 2021. I think it sells for $149 for the student/home user. Visit Microsoft's website for details.