Insert / 3D Object / Simple Extrude
It sounds like you want to extrude this collection of lines&arcs 8 feet. Being that you have Deluxe, you'll need to make the lines&arcs into a Polyline first. Select them, goto Modify/Join Polyline, then choose "Finish Join Polyline" from the Local Menu. Hopefully, if the endpoints are coincident, this will create a closed polyline. Now use the Simple Extrude tool to create a 3D object from the polyline. This is best done in a isometric view. Click on the polyline and move the cursor up or down. Tab and enter a value in the Height field. You also have a two-sided option, if needed.
Designer, Deluxe, (Professional, Expert, Basic), Platinum
Windows 10 Pro (1803), 64-bit