Hello Sophie224atkinson,
Thank you for using Apple Support Communities.
It sounds like you're having trouble receiving a Snapchat verification code on your iPad. You mentioned that you connected your phone number to your iPad. Prior to your iPhone breaking, did you take the steps here: How to forward SMS/MMS text messages from your iPhone to your iPad, iPod touch or Mac? If that's how you connected your phone number to your iPad, if your iPhone is not able to be powered on or connected to a Wi-Fi or cellular network, your messages won't be able to be received on your iPad.
If you're able to receive other messages on your iPad and are only having trouble with the verification code from Snapchat, you might want to reach out to Snapchat support for further help with the app.
Take care.