To back up everything I would make a copy of your Default profile folder to your Desktop.
The Default folder can be found at: C:\Users\[Your User Name]\AppData\Local\BraveSoftware\Brave-Browser\User Data. This folder will contain your bookmarks, extensions, etc.
After making the new Brave installation, you can replace the new Default folder with your backup copy.
For more details about backing up your data, see this topic: