Go to Solution.
Or use backup applications found in Play Store. (e.g Super Backup)
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Easiest way is to sync your contacts with your Gmail account. Once you set up your Gmail account on your new LG G2, all your contacts will sync back.
Another way is, please check if your HTC desire can export contacts as Vcard.
If yes, just export your contacts to Vcard format and trasfer it to G2 using email and import it from contact menu.