Hello there,

No, you can have all the passwords stored in Firefox if you synchronise your account.

Setting up Sync requires two parts: you must create an account on your main device, then sign in to your account using your other devices. Here are the steps in detail: https://support.mozilla.org/en-US/kb/how-do-i-set-sync-my-computer

Once your passwords are synchronised you can then go ahead and upgrade to Windows 10

Hope this helps!

It is best to backup your personal data locally and not rely on Sync because Sync isn't designed to be used as a backup.

• http://kb.mozillazine.org/Profile_backup
• https://support.mozilla.org/kb/Backing+up+your+information

These add-ons can be a great help by backing up and restoring Firefox

FEBE (Firefox Environment Backup Extension) {web link} FEBE allows you to quickly and easily backup your Firefox extensions, history, passwords, and more. In fact, it goes beyond just backing up -- It will actually rebuild your saved files individually into installable .xpi files. It will also make backup of files that you choose.

OPIE {web link} Import/Export extension preferences