Ask you uncle to return your property or file complaint in small claims court against him and storage unit. No attorneys are allowed in Small claims court unless you are a plaintiff and defendant hired an attorney.
This is obviously not a good situation (especially with a relative involved). Before you go to court, I suggest you talk to your uncle to understand what his thinking was in taking your belongings (did he think he owned the property, or was he claiming property to settle a debt?). Can you negotiate the return of your property? You might also talk with the storage shed owner who leased you property to understand what the owner was told. You might need help with this (friend, family, or attorney).
Your legal options are not always the best options. However, if you have property taken from you that was rightfully yours, then you can possibly sue the storage shed owner for breaking your contract (assuming you had a written contract, but if not, the claims get more complicated), and you can may be able to sue your uncle for taking your property. All of this will cost time and money, so you may want to consider the value of the property versus the stress and cost of pursuing legal claims.
Assuming your property loss was worth less than $10,000, then small claims court would be the right place to go. You can be represented by an attorney if you wish. For all the details, see --
This answer or response should not be considered legal advice, and does not create an attorney-client relationship. If you have further questions, I would be glad to discuss your situation further. I can be reached at US - (801) 746-6300, or online at -- http://www.lewishansen.com/attorneys/robinson.html