Hello Simrin, if you want to apply in US law school then you need to have an undergraduate degree from an accredited university or an acceptable foreign equivalent.

If you have UG Degree from a foreign university that US universities are willing to accept then you'll not be needing to take SAT (as it's for UG admission). 

If you do not already have an undergraduate degree and you wish to obtain both a law degree as well as an undergraduate degree in US, you'll need to - 

1. Take the SAT

2. Get admitted to a US University 

3. Study for about 4 years

4. Graduate with a Bachelor's Degree

5. Take the LSAT

6. Apply and get accepted in law school

7. Study for about 3 years 

8. Graduate from law school with a J.D.

In simple  words, Law School in US is a 3 year graduate degree that you begin after completing a 4 year bachelor's degree. You take SAT during your junior or senior year of high school to get into an UG program. You take the LSAT,  at the earliest, about 4 years later.

Best of luck!