Yes, immediately change your Apple ID Password. On the new laptop, make sure you install the newest version of iTunes V12.7.3. Sign into iTunes using your now changed Apple ID password and connect your iPhone via USB to lightning cable. You'll be asked to authorize your laptop for your iPhone and if you use two factor authentication, you'll be sent a code to use to authorize with. Your new laptop will download the drivers for your iPhone and you should be able to back it up.
This link also help you: How to move your iTunes library to a new computer - Apple Support