CSU eligibility index = GPA * 800 + SATRW + SATM (you can super score SAT).
So yours would be 3.10 * 800 + 1350 = 3830.
Some campuses like SJSU use an engineering-modified one which = GPA * 800 + (SATM * 3 + SATRW) / 2 .
SJSU publishes its past thresholds. For fall 2019, the thresholds were listed at http://www.sjsu.edu/admissions/impaction/impactionresultsfreshmen/ . AE required 4150 and ME required 4100 on the engineering-modified index. Of course, thresholds could change this coming year depending on application volume and strength.
Other CSUs that publish past thresholds are listed at http://talk.collegeconfidential.com/california-state-university-general/2150136-csus-that-publish-past-admission-thresholds.html