Hi Naomi,
Unfortunately, Microsoft removed that feature when they rebuilt the taskbar in Windows 11, and it now only supports being positioned at the bottom. According to Microsoft, allowing the taskbar to be moved would require rewriting how every element behaves in different orientations, which would take a lot of resources for a feature used by only a small number of users. For heavy users and those who are used to a different taskbar position, this change would definitely take a lot of adjustment. That said, I highly recommend using this third-party app as a workaround. This should allow you to place your taskbar on the side of the screen.
Disclaimer: This is a non-Microsoft site. The information seems reliable, but be careful with ads. Research any product before downloading.