Hi Jessica, you can use an SMS backup app for this. Just go to the Google Play store, search for "SMS backup" and install any one of the free ones that come up in the search results. I highly suggest trying out at least one of the apps for yourself and deciding which one is best for you based on your needs. They usually have the option of saving all messages to a .zip file as backup which you can then copy to your SD card when you're done. Of course when you want to get all your messages back on your phone again, you have to use the same SMS backup app that you used to save them. I hope this answered your question!