How do i get a copy of my grandfathers trust fund ? He died in 2001, which my father,deceased, changed it illegally. How to get copy of this as well?

grandfathers trust was named the herman family trust fund. It stated beneficiaries to be his daughters including my father. I believe it stated that the recipients maintain the trust living off the interest. It could be added to but not changed . Beneficiaries were me and my brother. I have learned that my father changed the trust fund to THE STANLEY CHANSON trust fund for stanley chanson with his son as beneficiary. No will is known to exist. I became seriously disabled after brutal beating by brother.He is listed as retarded and left real estate property in his name. Is this legal? I need a copy of the original trust and the changed trust to pursue my fair share as intended by grandfather. how do i find out where filed to obtain copies of each trust fund.