Trying to create the reverse of this Part for Gageing (Mold Tools)

Hey Everyone,

I am working on a gage. I have the part that I need to create a cavity or the reverse of this part. I am having some difficulties. I have tried many different approaches. PLEASE HELP I have attached the part, and a below is a picture of the part. I want to be able to sit this part in the cavity or reverse of this part. Can anyone help or give some advice.

SolidworksPlastics And Mold Design