How do up load my music from my iPad to a new apple commputer?

You should be able to copy iTunes purchases from your iPad to your computer's iTunes via File > Transfer Purchases (File > Devices > iTunes Purchases if you have iTunes 11 on your Mac). For music from other sources (e.g. CDs) you will either need to copy them over from your old computer (copying music), from your backup, or you will need to use a third-party program to copy them from your iPad - there are some programs listed half-way downthis page.