And you're an intern at a full blown studio?????
Do they let you plug stuff in?
Not to be snide, but this knowledge is very very basic recording 101.
1. NEVER plug a mic pre into another mic pre. WHY? Noise floor and you defeat any improvements the second outboard pre might make since its signal will be reduced to the signal of the LAST device in the chain.
2. M-boxes have LINE INPUTS. Why? They are used as interfaces for outboard devices in some cases.
3.A mic-pre is exactly what its label says it is. It is a preamp built to 'amplify' a signal from a low output device, (like a mic) into a higher voltage input such as a recorder/console/line input etcetc.....
4. There are literally HUNDREDS of mic preamps available. In all price ranges, colors, shapes and sizes. They all do essentially the same job, some do parts of this job better than others, some do it differently. Knowing which is best for what your intention is, is the part that becoming a recording engineer encompasses.
5. Knowing how best to use such a device is parallel to learning what it is and why it does what it does to all sorts of sources of sound.
Since you are an intern at an established recording studio in the Chicago area, I would hope that you are paying attention to these sort of details when you have the opportunity to witness the goings on in sessions. THIS is the only real way to knowledge about this craft.