This has changed in 19.
"If you have a different directory on the new computer you can use Tools - Library Tools - Rename, Move & Copy - Find and Replace to change the path. If you do the Find and Replace, I would suggest trying it on an album or two first, before doing the whole library."
It's similar but you can't do a Find & Replace on Filename field any longer; just make sure you use Update Location (as opposed to Copy, Rename, etc.)
cheers!