When I plug my iPod into my PC at school, it asks to format the device. Does this mean that it will erase all my music? How can I set my iPod so that I can move files from the PC onto my iPod and then onto my Mac at home. Thanks in advance to everyone.

mac 24.7.365

First of all, you aren't going to be able to transfer music
between two different iTunes libraries no matter what I tell
you after this, but if I understand correctly, you just want
to use your iPod as a portable hard drive for the PC and
Mac and as an music player paired with iTunes: Mac.

To do this, you will need to first plug your iPod into a PC
and run the iPod for Windows updater to update your iPod
to a Windows version of the iPod firmware. This will erase
all of your music from your iPod, but if your music is in
iTunes on your Mac, it will sync next time you connect it
to your Mac. Because iPod for Windows firmware formats
the iPod as FAT32 (which is readable by both Windows
and Mac) and not HFS+ (Mac only), an iPod formatted with
the Windows firmware will work on both Mac and PC.
Once you've updated your iPod on a PC, just plug it into
your Mac, open iTunes (iTunes will recognize it and pair
with it if your iPod is not already connected to another
iTunes library), and all of your music will be synced to
your iPod. You can now use your iPod for music with your
iTunes library, but because Windows and your Mac can
read FAT32, you can use it to move files between Macs
and PCs as a portable firewire harddrive.

Hope that helps,
Morton