How to get Word and Excel to work on MacBook Pro (Late 2008) running OS X 10.11.6 El Capitan?

I have an iPad Pro 12.9 inch that I use for everything. But Word and Excel are limited in the iOS 13 where I can’t do mail merges in Word & Excel (there’s no “Mailing” menu tab in Word, for example). So I got an old MacBook Pro that says it’s from late 2008, has a CD/DVD drive, etc. Updated the OS X to 10.11.6. I think that’s as high as it can go. In the App Store, I try to Get Word for Mac and it says I need OS X 10.13 or higher to get Word and Excel. Is there a work-around? Such as using my MacBook and Office online with OneDrive?