I’m not using V-carve im using Vectric aspire. Its a different program from the same company: the post processors and everything about it its the exact same. Please read all the list. Dont use your mouse to scroll, use your down arrow key with your keyboard to go tru the list. There are 2 grbl entries, you want this entry: Grbl (mm) (.gcode)*
If you still could not find it: download this and add it to your postP folder in v-carve and then manually add it. *You should not need this GRBL is there by default