Drag and drop targets to one target, in a specific order.

Hello Jennifer, I guess you're looking for a sequential drag and drop just like the default sequence drop down that's available in Storyline.

The default drag and drop wouldn't suffice your requirement within a single slide since you want this to be in a specific order. So, I suggest you to build a custom drag and drop by creating pick many interaction which is available in freeform.

Please share your SL project here so that someone can assist you with a better possible solution by reviewing your file.