In 2008 my husband passed away soon after my sister in law was granted temporary guardianship of my children due to a recommendation by cps. Now I am trying to terminate her guardianship and regain guardianship of my children . How do I do this and can I please receive any free legal assistance?

Whether you can receive free legal assistance depends on your area. I would check with local law schools, many run free clinics.

The first place I would start is with the caseworker in charge. Since you don't state why you didn't get custody when your husband died, we can't really tell where else to begin. The caseworker can probably explain what you need to prove to CPS to regain custody. You then go from there.

in 2008 my husband passed away soon after my sister in law was granted temporary gaurdianship of my children due to a recomendation by cps. now i am trying to terminate her gaurdianship and regain gaurdianship of my children . how do i do this and can i please recieve any free legal assistance?

Guardianship may be terminated only by court order.
You can go back to court and ask for the guardianship to be ended and the care and custody of the child returned to you.
You have to prove that the circumstances are changed.

We need more info... there are some red flags.
My concern is- why have you not been in touch on a regular basis with court and CPS case manager. Usually there is a plan in place to reunification or not. Two years is a long time to be in one placement without looking at reunifying. You do need to talk to your case manager. You should have already been given a list of things that need to be accomplished by you in order to regain custody. So, hopefully you have some of these answers and contacts to get some help.