Music on iPad Pro

To add to Lotus's excellent answer, at around 5 or 6MB average per track in most cases, you can fit around 80,000 tracks in 512GB of storage space.

The higher the quality and length of a track, the less tracks you can fit.

The absolute number of music tracks that you’ll be able to store will be heavily influenced by the compression/encoding of the music. AAC is more efficient than MP3, but is less flexible. If using 320kb MP3 (the highest bitrate / least efficient), with 512GB at your disposal, you’ll need to have a massive music library to exhaust the available capacity.

Consider that your iPad will likely be used for other purposes - and some of your storage capacity will be used for other purposes - not least the iPad requiring a small proportion for iPadOS itself. 512GB is still a substantial platform.