I have a circuit diagram that requires an inductor labeled L1. However, I couldn't find its value in either the MCU datasheet (attached) or the schematic (attached). Can you help me determine its value?

 

That inductor is there to block noise from your digital supply getting into your analog supply that is derived from it. It's value depends on how much noise is on the digital supply and how much noise you can tolerate in your analog supply. A significant aspect of the this involves what the frequencies involved are. In many situations, a ferrite bead (which is essentially a lossy inductor) is adequate.