What will happen if I possessed stolen property, without any knowledge the property was stolen?

Lack of knowledge of the stolen status of the property is a defense to this crime.? You have to know or should have known that it was stolen.

California State Penal Code Section 496 Receiving Stolen Property. 496. (a) Every person who buys or receives any property that has been stolen or that has been obtained in any manner constituting theft or extortion, knowing the property to be so stolen or obtained, or who conceals, sells, withholds, or aids in concealing, selling, or withholding any property from the owner, knowing the property to be so stolen or obtained, shall be punished by imprisonment in a county jail for not more than one year, or imprisonment pursuant to subdivision (h) of Section 1170. However, if the district attorney or the grand jury determines that this action would be in the interests of justice, the district attorney or the grand jury, as the case may be, may, if the value of the property does not exceed nine hundred fifty dollars ($950), specify in the accusatory pleading that the offense shall be a misdemeanor, punishable only by imprisonment in a county jail not exceeding one year. A principal in the actual theft of the property may be convicted pursuant to this section. However, no person may be convicted both pursuant to this section and of the theft of the same property. To be convicted of receiving stolen property the prosecution has to prove that you knew the property was stolen.

That depends how good your lawyer is. FYI everybody who is charged with this says the exact same thing: "I didn't know it was stolen."

Sounds like you may have a valid legal defense. You can only be convicted if they prove beyond a reasonable doubt that either you knew the property was stolen or you should have known the property was stolen. Retained an experienced criminal defense attorney to represent you.