The short and simple answer is you need a degree in physics however if you’re already in an institution that does not offer a degree in physics you may want to consider the degrees below or possibly consider transferring to a university that offers your degree!
Bachelors in physics
Bachelors in science concentration in physics
Bachelors in science engineering.
Loriel recommends the following next steps:
The mandatory classes for a physics program can vary quite a bit, but I'd expect most institutions have a similar standard of study requirements covering core physics topics such as classical mechanics, electromagnetism, basic quantum mechanics, and such. I'd also expect a core of mathematics requirements to support the physics - calculus, complex numbers, vector calculus, etc.
Beyond the core subjects, I'd then expect you'd need various additional optional physics-related classes - you might have a minimum number of physics-related classes to achieve, for example. You'd generally be able to use these to specialize your learning in certain areas of physics - for example taking a bunch of cosmology, relativity and astrophysics classes; or something else like nanomaterials, computational physics, engineering and such.
If you combine Physics with Math and Computer Sc, - you can work at NASA, Software Industry and high-tech manufacturing including Robotics.