Both have mini-SIM slots, so you can simply swap them.
Micro-, actually. The common SIM cards today are mini-SIMs. Full-sized SIMs are the size of a credit card. (The card that a SIM card comes in is designed to fit really old devices that take the original full-sized SIM, but I doubt too many are in use anymore.)
iPad 3G 64 GB
Data plans: Bell (.ca), Rogers (.ca), AT&T (.us)