My mod_rewrite code in htaccess caused the page to not load

I have horrible URLs like this:

http://example.com/subfolder/index.php?a=1&b=1&token=8d519decbe60db44154b1fbc8c553ac4

I am trying to make it look like this:

http://example.com/subfolder/menu/1/1/#/

But this code is causing the page to crash/not be found or something:

RewriteEngine on
 
 RewriteCond %{QUERY_STRING} ^a=([0-9]+)&b=([0-9]+)&token=([A-Za-z0-9]+)
 RewriteRule ^subfolder/index.php /menu/$1/$2/#? [R=301,L]
 

I put this .htaccess file in my root folder example.com/.htaccess, do I need to put it in the subfolder?

I'm getting 404 page not found error !

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