My understanding is that in the unlikely case he is sentenced to prison, yes, the Secret Service would have to accompany him there.
If I were to venture a guess, I have my doubts that he will actually serve time in prison. The security issues that would raise are just too great and having an ex-president in that situation raises a bunch of issues both for his own personal safety, the safety of secret service agents, and the safety of other prisoners.
I suppose they could put him in the Supermax where he would have little to no interaction with other prisoners.
My bet is he will be sentenced to house arrest and will be required to stay either in his rooms at Trump Tower or at Mar-a-Lago, with restrictions on his Internet and phone use and visitors restricted to immediate family. That's probably as good as can be reasonably hoped for.