The default location for the Music library is ~/Music/Music. If this folder already exists you may want to delete or rename it before attempting to import your iTunes library. You can press and hold down option as you launch Music to get an option to choose or create a library. If you select an ITL file you are then prompted for a location to save the converted library. Use ~/Music/Music for the standard location. Once the library has been converted Music will be using the old iTunes path of ~/Music/iTunes/iTunes Media. You can reset the media folder to ~/Music/Music/Media and consolidate the library if you have space to temporarily double up on the space used, or if not you could try relying on macOS' generally ability to keep track of files moved around on the same volume and move and rename the iTunes Media folder from ~/Music/iTunes/iTunes Media to ~/Music/Music/Media, then update the path to media folder under Media > Preferences > Files.
You should follow similar steps to import the video content from your iTunes library into the TV app. If you have any audiobooks, books, or podcasts these can be imported directly into their respective apps. Books and Podcasts both make use of hidden library folders so once any content has been added to those it would be referencing the files in the old iTunes Media folder.
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