There's an app called "SMS Backup And Restore" (the one I use specifically is by 'Ritesh Sahu'). Download it on your Evo 3D and it will save your texts to the SD card and then when you put the SD Card in your Evo LTE, also download the app and use the restore function in the app. I always use this and it never fails me!
Hope this helps!!
There's also SMS Backup+ that links to your Gmail account and does automatic backups daily.
I dont understand what u want to explain...? I just want to know if i can save my txt msgs. PLEASE READ MY LAST Post. Thnx