http://fdiland2k23drdjqmxgmnjmzb47s3ildy5wyh5t4gk2tgjo3yfdffyyd.onion/kemono/thread/2.html
The filename is generated when you upload the pic and it includes a timestamp
(see https://archived.moe/cm/thread/3925527/#3927116) but since you can wait a while before sending a tweet, or even schedule it for later, this timestamp isn't directly related to the tweet id.
To make everything worse, many artists change their name at random and old names don't get redirected to the new ones, so it's not a very useful format all things considered.