Object > Generative > Gen Shape Fill…

You can follow along with a sample file from Adobe’s helpx.adobe.com site.

Select the shape and/or multiple shapes you’d like to fill before going to the menu command above, using the Generative pop-up at the bottom of the Toolbar, the button at the bottom of the Properties panel or in the Contextual Task Bar, then enter a prompt. If ‘Suggestions’ is turned on, several options will appear as you type.

‘Shape Strength’ determines how closely the generated artwork will follow the edges of the selected shapes. ‘Detail’ controls the complexity of the generated vectors. The artwork will be created on a new sub-layer, retaining the original shapes untouched below.