One thing I've learned after having the Internet for a couple of decades, you might change ISP's and when you do your email from the preceding one are gone.  We moved to gmail so that no matter what ISP we have we will have access to our email. 

https://support.cyberpowerpc.com/hc/en-us/community/posts/19989421896083-How-to-Import-Windows-Live-Mail-to-Thunderbird

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Mailvita EML to MBOX Converter Tool is simple method import Windows Live Mail to Thunderbird. This utility is  convert bulk WLM files to MBOX file format. This application is supports all email clients of MBOX file such as Thunderbird, Apple Mail, Poco Mail, Sec Monkey, Eudora, etc. Supports all Mac and Windows OS versions. Download the free demo version of the application.

Visit here: https://www.mailvita.com/kb/solution-to-convert-eml-to-mbox-on-mac-windows/