Try the function "Tag - filename" (it's in the toolbar - move the mous cursor over the buttons or select the function from the menu Convert or press Alt-1)
The subsequently opening subidalog has an entry field for you to enter a mask which can be filled with tag-variables and text. To find the correct syntax for the variables: use the button with the right arrow to get a list.
A mask very often looks like this:
%track% - %artist% - %title%
If you want to have the same number of digits for the tracks:
$num(%track%,3) - %artist% - %title%
As there is also a converter that lets you read a filename and extract tag information (if there is any), it may be a good idea to use a separator between the fields that usually is not part of a band name or so.
I prefer the underscore _
So your mask may look like this:
$num(%track%,3) _ %artist% _ %title%
$num(%track%,3) _ %artist% _ %album% _ %title%
Play with it