How can I get songs off my ipad to my ios?

That will depend on your system versions on the iPad and the iMac.

• If iPad and iMac are compatible with iCloud, you can save your GarageBand song to iCloud as described on this Help Page: See: Use iCloud with GarageBand
• If you do not have iCloud, send your iPad for GarageBand song to iTunes as described on this Help page: Share GarageBand songs

Send a GarageBand song to iTunes

• Tap My Songs, then tap Select.
• Tap the song you want to send, then tap the Action button .
• Tap Share Song via iTunes.
• Do one of the following:
  • To send the song as a GarageBand song, tap GarageBand.
  • To send the song as an audio file, tap iTunes, then tap Share.
  After you tap the iTunes icon, you can choose the quality of the file GarageBand sends to iTunes. You can also add artist, composer, and title information that appears in iTunes.
• Sync your iPad with your computer.In iTunes, the exported song appears in the Documents list in the File Sharing area when GarageBand is selected.
• Do one of the following:
  • Drag the song from the GarageBand Documents list to the Finder.
  • Click Save As, navigate to the location where you want to save the song, then click Save.

You can open the GarageBand song in GarageBand on your Mac, or play the audio file in iTunes (or any compatible audio application) on your computer. GarageBand songs cannot be opened on a Windows computer.

You can also send the song by Mail:

Send a GarageBand song via email

• Tap My Songs, then tap the Action button .
• Tap Share Song via Mail.
• Enter the artist, composer, and album name if you wish, then tap Email.An email message appears, with the song as an attachment in AAC format.
• Tap the To, Cc/Bcc, and Subject fields to edit the recipients and the subject of the email. To choose recipients from your Address Book, tap the Add Recipient button.
• Tap the body of the email to edit the message text.
• When the email is ready, tap Send in the upper-right corner to send it.You can’t send the email until you add at least one recipient.