You were entrusted with company property. You were required to return it upon your dismissal or departure. Apparently you failed to do so. Yes,the company could sue you in civil court. I don't think this is a contract axe, although it might be considered a bailment.
Either way, the company decided to file criminal charges for conversion. That's just a form of theft. You unlawfully took the property of another with the intent to permanently deprive.
I suggest you appear, plead not guilty, make no statement, offer no excuse, and provide no explanation. Hire a lawyer, or ask the court to appoint one to represent you. Meet with the lawyer, and follow his or her instructions. Stay out of additional trouble, and this won't be that big of a deal.
Whatever you do, don't blab, and don't try to talk your way out of this. ANYTHING YOU SAY, CAN AND WILL EVENTUALLY BE USED AGAINST YOU IN A COURT OF LAW. So, for YOUR benefit, resist the temptation to open your mouth. That is how fish get hooked!!!
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