my mac versos 10.15.7 is not accept microsoft office files

Microsoft documents have nothing to do with the operating system version, but you cannot install a current version of Microsoft 365 or Office 2021/2024 for Mac into Catalina because Microsoft only supports the current (Tahoe) and two previous (Sequoia, Sonoma) operating systems for new installations.

Alternatively, you could install the free, current LibreOffice Suite, SoftMaker's Office 2024 (paid, but free trial), or maybe even a version of Office 2019 for Mac from Microsoft provided you have a compatible license. The previous two linked suites are MS Office clones with a long history of document compatibility. The user interface on Softmaker's product more faithfully reproduces the current Microsoft style of MS Office.