Many different .pict files exist, so it's hard to give a specific answer for any kind of pict export, but AI format is certainly related to Adobe Illustrator, which limits any potential conversion options greatly. If you are not sure about the origin or type of .pict file you most likely have to retort to trial and error method until you are successful. Pretty much every .pict file is raster though and Illustrator works with vectors, so in any case, the conversion won't certainly be optimal way how to create Illustrator graphics.
Updated: August 21, 2023