Hi! I wanted Windows 11 to look like 10, but broke the Explorer search bar. Can anyone please help?

We won't recommend using unofficial solutions and instead if you are looking for a customization method or feature missing in the Windows 11, make sure report it using the Feedback Hub app. Since you used a method from non-Microsoft website, you may ask them (since they create it).
Meanwhile, you may open the Command prompt as administrator and then type the following command:

sfc /scannow