: Reach out to the software vendor's customer support. They can provide your serial number if you've lost it or if there's an issue with your purchase record. Be prepared to provide proof of purchase or details about your account.
: A professional converter by FontLab ($97 commercial) that specializes in converting Type 1 to OpenType. fontxchange serial number mac
If you absolutely need FontXchange for legacy workflow reasons and you already own a license, reinstall from your original disk/download and enter your existing serial. Otherwise, let it go. : Reach out to the software vendor's customer support