Is it possible to copy Storm King's Thunder maps to a custom game?

I purchased this module, not realizing there was a difference between Module and Add On. I wanted to use some of the maps in my custom campaign, then run the whole thing later for another group. 

It would require the use of the  Transmogrifier which is a pro subscription feature to move maps from a module based game to an existing game.

You can use the transmogrifier to copy the entire page the map is on, but here is an alternate method: Use the selection tool and click on the map, press Z to zoom. Right click on the zoomed image, "save image as", choose save location. You'll get a .jpg on your hard drive which you can then drag into your custom campaign. The now uploaded image will count against your storage limit.

Transmogrifier is probably what you want as it will bring the tokens, dynamic lighting, gm notes on the map, etc along with it.  You will want to transmogrify over any characters you want to use when you do it.