Thanks for the help! It’s important for audiobooks to be in order so I can’t just assign them any track number. How can the software distinguish which file is the first, second, third etc? Is there more info on this or am I out of luck?
I don't know what the filenames look like - usually they are a pretty good criterion to sort by.
You can sort by any field that contains data and some of the file properties as well, e.g. the creation date would be something like that.
And once the files are in the correct order, you use the numbering wizard.
If there is nothing to be used for sorting, you can move the files up and down in the list with alt-drag&drop.