I used SMS backup+ to transfer sms/mms from the old phone, requires a google account.
But in the default “messages” app on the FP3 the restored sms/mms messages doesn’t show up so I installed another one from playstore that did find them.
I’ve not found any sms/mms app that I really like yet, so going with the least irritating one for now, SMS from android 4.4. ( It has advertisement in it 
)
Oh, just remembered, before restoring sms/mms, go to settings and uncheck the “only restore 500 sms” or something like that if you have more than 500.