Import messages from Icedove to Thunderbird

[Markos]

Hi,

I've just installed Debian 9 (stretch) and I'm trying to import folder 
with messages from Icedove 38.5.0 at my old PC (running debian 8) to my 
new PC with Thunderbird 52.8.0.

In Icedove I select a folder and Tools -> Import/export in mbox/eml 
format -> Export folder

And save the file in a pendrive.

In Thunderbird I select Tools -> Import -> Messages -> Mail -> Next

But appear only the message: No application or data file to import

And no option to select the file that contains the contact list as in

http://write.flossmanuals.net/thunderbird/migrating/

Please, any tip?

Thanks,

Markos