General Discussion

Your spreadsheets will open in later versions of MS Office, including 2024. They may open in compatibility mode (first link) and you can convert them to the newer xls if you need to use all the 2024 bells and whistles(second link).
https://support.microsoft.com/en-us/office/use-excel-with-earlier-versions-of-excel-2fd9ffcb-6fce-485b-85af-fecfd651a5ac]
https://support.microsoft.com/en-us/office/use-excel-with-earlier-versions-of-excel-2fd9ffcb-6fce-485b-85af-fecfd651a5ac#bm4]

I recently bought both 2021 and 2024 and have no problems but my oldest spreadsheet are from 2007.