Think like a mathematician. Paulo has forgotten the 4-digit number that allows him to unlock his case. He knows that the number:

Is less than 3000
Is divisible by 3
Has a tens digit that is divisible by 3
Has a hundreds digit that is divisible by 3
Has a ones digit that is bigger than the tens digit
Has a ones digit and a thousands digit that are not multiples of 3
Has no zeros.