I don't think you can, since your neutral file doesn't even have the line no.
From where did you get the neutral file?
IF you have the original CAESAR II file that has the line no, perhaps you can still recover your line no. Try to find the .c2db (you may need to extract it from the original CAESAR II archive), rename it to the new CAESAR II file. You may be able to do this if the original and the new files have the same number of elements, node numbers, maybe the same order too etc.
Other than that, I think unless you know how to manipulate databases, you're out of luck. I could be wrong.