I went through this exact same thing with my mom last year. Please tell your uncle not to pay anyone anything upfront.
Legitimate firms do exist, but they typically work alongside law enforcement or legal teams, and they will give a realistic assessment rather than promising a 100% guarantee.
Your best first step is filing a report with the IC3 (if you are in the US) or your local cybercrime unit. Be very wary of anyone in your direct messages right now recommending specific fraud recovery experts.