Hi @BABY_JOJO
You have two options to upgrade to the latest version:
1) You can outright buy Office Home & Student 2021 (for Excel 2021)
This includes a one-time purchase for a single device.
2) Purchase Office 365 Subscription (if you pay the monthly fee you will always get the most up-to-date Office product)
This is a monthly subscription and allows you to install on five devices.
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If this is helpful please accept answer.