To do so this is easy. Note: Your struckd game has to be a draft. So first download it by going to Game Exporter and then download it from there and then extract

it all to downloads and then open unity and make a 3d game. Then when the game is loaded then in the top bar click "window" and click Package Manager and in the top bar click the plus icon and use the from dick option and in the folder you extracted open the "package" file and the struckd game exporter will be installed in your game. After it loads close the package manager and on the top bar click the "struckd" button and click inport on the game you want to be inported in unity and then your game is in there! Thanks for reading!