I need more tracks!

Your preamp needs to have 1/4" output jacks which channel all of the mic inputs into these two outs. This isn't typically how a mic preamp is set up however. They often will have 2 ADAT outs which output all the inputs in stereo or some other configuration. You may have one that can do this, but if not you'll probably end up needing some kind of basic external mixer which can handle all of the individual outs from your preamp through the mixer's inputs and then you'd run the main outputs from your mixer into the two inputs on your Tascam DP-01.