After registering an email and password to your LINE account on your smartphone, you can carry over all your previous LINE account information when you change your mobile device or phone number by performing LINE User Login on the new device or phone number. You will also be able to use the PC version of LINE and LINE Store in regions where it is available.
Your friends list, purchased items, and game results are associated with your LINE account. To prevent any disappointment, please register an email address at your earliest convenience if you have not done so yet.
Please see the following for a detailed guide on email registration.
How do I register an email?