You can swap the normals with ALT + N.
You can also see it if you click on the arrow at the top right (see picture) and activate Face Orientation in the small menu at the bottom. Red on your faces is bad, blue is good, the right side so to speak - you must be in edit mode for this
With ALT + N you will get the Normal's menu and you can choose "Flip" for the Normals to get flipped. Keep in mind if there are Normals pointing the right way, with the Flip command it'll flip that Normals in the opposite direction as well. So you can also use the shortcut Shift + N to recalculate the Normals and Blender will just intelligently fix them for you.