Hi Denise,
If your PC is currently running Windows 8, first check whether the hardware meets the requirements for Windows 11.
Microsoft states that Windows 11 requires, among other things, a compatible 64-bit processor, 4 GB RAM, 64 GB storage, UEFI/Secure Boot capability, and TPM 2.0.
Also, Microsoft documents the direct Windows 11 upgrade path as requiring an eligible device already running Windows 10 version 2004 or later, so you shouldn't expect a direct in-place upgrade from Windows 8 through Windows Update.
I recommend backing up your important files first and checking your computer manufacturer's specifications against Microsoft's Windows 11 requirements. I've attached some information here which should help:
Microsoft reference:
Windows 11 system requirements
If the computer doesn't meet those requirements, Microsoft recommends considering a newer PC that supports Windows 11.
I hope this helps. All the best.
David.