Quicksurface – How to make my mesh as solidbody

Hi all, i scanned a motorcycle part which im trying to reverse engineer.
I used Fit surface on whole 3d scanned mesh and later trimmed to get final model.
But i dont know how i can thicken it and convert it to solid body?
I tried something called “Saw Surfaces” because i thought it could saw all fit surface meshes i did earlier so i can thicken it
But when i want to thicken the part it always says failed

My question is, how can i make a solid body out of one single sided mesh i achieved with only option Fit surface?

https://preview.redd.it/dla1a4dsktae1.jpg?width=4496&format=pjpg&auto=webp&s=2cb3b1363efc16e232ea5a22087ec52bc9e6cacf