By default, Blogger adds ?m=1 to Blogspot posts URLs when viewed on mobile.
After switching from Blogger to WordPress, anyone that access such links will land on a 404 page. Hence, after migration to WordPress, you will likely see lots of 404 errors listed in Google Webmaster console that are related to this Blogger mobile view url.
Guess what?
You don’t have to redirect the links one by one. You can fix it all with a code.
All you need to do is to add the code below into your .htaccess (hypertext access) file, after the RewriteBase / line
#blogger mobile url-fix
RewriteCond %{QUERY_STRING} ^m=1$
RewriteRule ^(.*)$ /$1? [R=301,L]
#blogger mobile url-fix-ends
Below is sample .htaccess file with the code in it :
Ensure you save the file.
I hope this helps.