To redirect the folderA to the folderB, you want to redirect as in your comment in the other answer.
This will redirect /folderA/blabla/blalba/bla/t_2345
to /folderB/blabla/blalba/bla/t_2345
RewriteRule ^/folderA\/(\w+)\/(\w+)/(\w+)\/t_(\d+)$ /folderB/$1/$2/$3/t_$4 [NC,R=301,L]
If the number of folders changes, but they all end in t_digits, you could look for anything between the folderA and the t_digits. e.g., this will redirect /folderA/abcdef/t_1234
to /folderB/abcdef/t_1234
RewriteRule ^/folderA\/(.+)\/t_(\d+)$ /folderB/$1/t_$2 [NC,R=301,L]
You may have to adjust whether to keep the leading slash, depending on how things are configured. Also, your question has a trailing slash, but the comment examples don't, so add or remove a trailing slash depending what you really need.
EDIT:
A side note about the permanent redirect. While debugging this, use [NC,R,L]
without the 301. When the redirect is permanent (301), the browser often caches a previous rule. When done testing, change it to permanent. See number 2 and 3 in this answer: https://stackoverflow.com/a/9204355/292060