Sunk is more optimistic than I am about using a file converter.
The email system was never designed for viewing mail in a web browser. It was designed around the idea that people would use a totally different program (i.e. a dedicated email client) to send and receive mail. Webmail services (such as Gmail) only came later and, although they can be really useful, are always only a 'second best' to using 'proper' email. So I'm going to suggest that you try opening your eml files in a proper email app:
Suggestion 1: Right-click on an eml file and select Open With > Mail. (i.e. the Windows 10 Mail app).
Suggestion 2: Install Thunderbird.
https://www.thunderbird.net/en-GB
then right-click on an eml file and select Open With > Thunderbird.
Suggestion 3: Install Thunderbird and try this method to import the files into the program:
https://support.mozilla.org/en-US/questions/1029444