In the Star Wars prequel trilogy, midichlorians are introduced as microscopic organisms that live within the cells of living beings and allow them to connect with the Force. However, in the original Star Wars trilogy, there is no mention of midichlorians, and it is not clear what Luke Skywalker knew about them.

In the original trilogy, the concept of the Force is presented as a mystical energy field that surrounds and penetrates all things, and it is through training and discipline that one can learn to tap into its power. Luke Skywalker, as a Jedi Knight, is trained in the ways of the Force by Obi-Wan Kenobi and Yoda, but there is no indication that he has any knowledge of midichlorians.

It is not until the prequel trilogy that the concept of midichlorians is introduced, and it is suggested that they are the key to a Jedi’s connection to the Force. However, even in the prequels, it is not clear how much Jedi know about midichlorians. Qui-Gon Jinn is the only Jedi who seems to have a deep understanding of midichlorians and their importance, and even he is met with skepticism from other Jedi.

In the end, it is likely that Luke Skywalker did not know much, if anything, about midichlorians. From his perspective, the Force was a mystical energy that he had to learn to tap into through training and discipline. The concept of midichlorians, while it may have been important to other Jedi, was not central to his understanding of the Force.