The idea is fairly simple, but the details can make it complex.
The idea is to use Find+Replace to change the file path of every music track from what it is on PC1 to what it is on PC2. How much the two PCs differ determines how much of the path must be changed.
The ideal situation, which many (including me) seem to do, is use exactly the same path on every PC. This eliminates the need to change the path. On all my computers, my music library is on drive M:, and exactly the same path on drive M. I just copy my library from PC1 to PC2 and because everything MC cares about is identical, it "just works".
Or, if the PCs must have the library on different drives, it's good to use the same folder structure, so Find+Replace must only change the drive letter (C: to M:, for instance).
Or, if the PCs use different drive letters AND different folder paths, it's still very good to have the paths be identical at some point, so only the part that differs must be changed.
But if the PCs are not at all consistent in paths and folder names across tracks, there's virtually no reasonable way to use Find+Replace. There are other techniques, such as having MC start with the library as it exists on PC1 then re-import it on PC2, but potential risk of something going amiss.
If you're going to do a bunch of work, consider doing it just ONCE by changing both PCs to have identical MC library paths and ideally identical drive letters. I suggest not using the default library paths of MC or Windows. My library on every PC is M:\data\music -- nothing special about this, except it assures I'm in control of where this is. (Note that different versions of Windows put "My Documents" and "My Music" and other user data in different places (and in different folder names), which many years ago led me to ignore this and set up my own \data directory and put everything I care about in it.)