Saving all part & assembly into one Assembly file..

I recieved an assembly sent to me as a single file.. All the parts in the assembly were included internally in the assembly..

As I was working, I played with the "save part(in External file)" ... Now the part i've "save part(in External file)' is separated, and they would need path specific in order for SW to detect it...

Is it possible to put them back into that single assembly file? I've never worked with an assembly file like this =/

I'm hoping for some "pack and go" option that allow me to combine them all