You're misreading something. There is no Service Pack 3 for Windows 7. In fact, there's no Service Pack 2.
See "Step 6" here, especially the 5th paragraph: https://answers.microsoft.com/en-us/windows/forum/windows_7-windows_install-wininstalls/clean-reinstall-windows-7/0ae269fd-167e-423b-94ef-26133f89e10c
If following the instructions in Step 6 don't result in getting Windows 7 SP1, see: https://support.microsoft.com/en-us/help/15090/windows-7-install-service-pack-1-sp1
You want either
windows6.1-KB976932-X64.exe if you have a 64-bit system
windows6.1-KB976932-X86.exe if you have a 32-bit system