Hello Angela Melina,
It looks like there's nothing to lock anymore — Windows 11 redesigned the taskbar and the old "Lock the taskbar" option seems to be gone. The taskbar appears to be locked by default now, so you can't really drag or resize it like you could in Windows 10, which probably means you're already covered without doing anything.
The official Customize the taskbar page walks through everything you can still change (alignment, pinned apps, badges, auto-hide, system tray), and there's no lock/unlock option anywhere in it, so it looks like that setting has been removed: Customize the Taskbar in Windows
If what you're actually after is the old behavior — resizing the taskbar height or moving it to the side/top — that doesn't seem to be built into Windows 11 anymore, and the only way to get it back is probably a third-party tool.