Sheet metal help

I am trying to design this box for a project that I am working on, and I need mirror what I did on one side onto the other side, but I don't know how to do it. The to edge and merge option for edge flanges won't let me. Any help is appreciated, I am ok with redoing the model if there is a better method to model it!

I am trying to get something like this

SolidworksSheet Metal