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I am sorry to learn of this situation. Unfortunately without a little more information I am unsure what I can assist you with today.
The law can protect you from fraud (did they misrepresent something to you - lie to you about a material element or fact in order to get you to agree to transfer ownership of your belongings), and the law can help you enforce contracts (if they agreed to pay you a certain amount of money or percentage of a sale, but now refuse to do so).
You can usually sue in small claims court to enforce these rights, unless the amount in question is very high, and you will not need a lawyer to represent you.
The law does not however protect you from a bad business deal - so if you sold the items for a low amount of money and later found out that you could have sold them for more, you cannot sue for that.