If the two three year sentences were to run consecutively, then it would be a total of six years. However, if the two three year sentences run, as you indicated, concurrently, that means that both sentences will be completed in a total of three years.
You have only 3 years on probation. The other 3 years is running at same time. On a first offender sentence you may be able to terminate probation after serving half your sentence if you comply with all conditions and get your probation officer to agree. when you have completed that part of your sentence you should consult with an attorney to file a petition for first Offender discharge.
In California concurrent sentencing means that one charge is subsumed within the other charges, so if one charge carries 3 years and the other carries 3 years, you would only serve three years on a concurrent sentence, whereas consecutive would be 3 + 3 = 6.