how to change default url format

First thank you for the product, all the migration works from vbRank are smooth and it works very well.
I have a question: I've chosen the DaniWeb format.
So the forum url is something like forum1.html and the thread url is something like thread123.html.
How can I change it into f1.html and t123.html? Since I want to make the url shorter, anyway they are meaning less

You can choose from several pre-set URL formats in your vBSEO Control Panel. This is the safest way to do this, since customzing the URL formats can break things if not done properly. Try out the pre-sets. There is at least one option that uses minimal URLs.