Hey Johnathon! Thanks for joining the platform!
No your Audio Interface is USB, so simply just needs to be plugged in with USB Cable.
PCIe Audio Interfaces are not very common these days.. if they are, more in very high-end studios..
A USB Audio Interface has many advantages, as you plug the audio interface via USB cable, so it can sit close on your desk. This allows you to turn up and down volume of speakers, headphones, and microphones very quick. More advanced audio interfaces also allow you to switch sets of speakers, or enable mono for testing your mix!
Your USB mic will plug in USB also, but it won't have anything related to the audio interface. (You'd need an XLR Microphone to use the mic with your audio interface, so for the USB Mic, you control all volume via Windows desktop.. or if your USB mic has a gain knob on it).
Same with your MIDI Keyboard, it is just USB. I have an in-depth M-Audio Oxygen Pro Help Area.
For speakers, these simply plug into your audio interface with TRS 1/4" cables (sometimes XLR.. but usually TRS 1/4), if you eventually get reference monitor speakers!
The biggest thing for the best performance in FL Studio is selecting an ASIO Driver. FL Studio ships with its FL Studio ASIO, but usually your audio interface's ASIO will give you a bit lower latency (you have to install driver from your audio interface's website, it usually doesn't auto-install).
Lastly, you may like the Essential Gear Needed to Make Beats course, which breaks down the music equipment, how to use and set it up, and how to save money!
To recap: No you do not need a PCIe card for your USB Audio Interface. This just plugs in via USB cable to your computer, and make sure to install the audio interface driver from your manufacturer's website!
