Retirement account liquidation by the previous employer, if I were to look for a lawyer what kind of specialty should I look for in the lawyer/firm

Hi, I worked for my previous employer for a little less than four years and during that time I contributed to 401(K) religiously, My company did not match anything. They provided a PCRA (Personal Choice Retirement Account). After I quit the company and established my own corporation I opened Individual 401(K) account with the same brokerage company. When I contacted the ex-employer about my PCRA 401(K) account. They indicated if I chose to I could still leave that account as is and operate without any issue, I did so due to lack of time. Recently, I got a letter from the ex-employer that they were making changes to PCRA account perhaps moving to another brokerage firm and I had two choices, either liquidate my funds or request for in-kind transfer which would allow me to move my existing PCRA to individual 401(K) as is. I did all the paper work a month in advance and submitted. Still due to someone''s negligence my account got liquidated without my approval. I need to file a suit.