Hi !
Stock data in Microsoft Excel is only available for Microsoft 365 subscribers. If you have a perpetual license of Office (2021, 2024...), the option will not appear.
If you have Microsoft 365 installed on your PC, head to File > Options > Trust Center > Trust Center Settings > Privacy Options > Privacy Settings, and make sure "Turn on optional connected experiences" is enabled.
Please let me know if you have any other question !