Received my migration letter and feel so worried

hi, I’m hoping people can advise please. I’m so worried about the letter I’ve received and how this is going to affect my benefits.

I am on old style ESA support group which should been reassessed last year but never was.

I also get pip higher rate both elements. I get child tax credits and child benefit and housing benefit and council tax benefit.

I am so worried about being reassessed and being found I have to work as I would just not cope with this. Does anyone know if I will automatically get the equivalent of the old style esa support group in my universal credit or do I have to reapply and get reassessed for this? Also does my pip stop and child benefit?

Also does anyone know if I will get back dated for the time period they say I will. It get any money for so say 5 weeks do they backdate to the start of the claim

I want to try and get as much information before I apply for the UC so hoping some people could kindly give advice

many thanks