Transfer of music to external drive

I have recently tried to transfer my library to an external hard drive and now when I try to access a track from iTunes

it cannot find the music and I have to find the track manually for iTunes, I have a lot of music (hence the need to transfer it to an external hard drive) and I cannot do this for all my. Can anyone suggest how I fix this?

最後更新：2017-09-09 02:31:17