Hi familyharding,
We understand your music library isn't syncing across all of your devices, and we'd like to help. To get started, can you let us know if you're an Apple Music or iTunes Match subscriber? These services should automatically sync content across devices when Sync Library is enabled.
Turn on Sync Library with Apple Music
Otherwise, the content will need to be synced from the iTunes Library on the PC to the iPhone and iPad, either over Wi-Fi or by connecting the device to the computer using a USB cable.
Sync iPhone with your computer
Please let us know what you find, and we'll continue helping from there.
Have a great day!