I can't find LINE IN - Audio Input Problem with a Mac Book pro early 2015

I'm trying to record on my Mac book pro early 2015, but the Line-In port does not appear. I only have the "built in Mic" option. I have plugged different kinds of mini jack in the only in/out port, with the device already turned on...and NADA.

You don't have a line in.

Per the Technical Specifications for your MacBook, it has support for a line out, but not line in.

Audio

• Stereo speakers
• Dual microphones
• 3.5 mm headphone jack
  • Support for Apple iPhone headset with remote and microphone
  • Support for audio line out (digital/analog)

^{Emphasis mine}

To get a Line-In, I suggest using a USB-DAC or a USB Mixer so you can get a proper line level input and output. In fact, I try not to use any of the built in audio ports due to their poor shielding and "economy grade" components. You'll get better results with a proper audio interface.