A little lost with 2.1 platform logistics

https://preview.redd.it/ijad3vr426hh1.png?width=1920&format=png&auto=webp&s=86d1139e8d228e8365bbd7bb5883d8cd1c5d5864

https://preview.redd.it/0lowp7y826hh1.png?width=1920&format=png&auto=webp&s=b1c568464c48da5b9184204d312a61469c8a55a1

Hi! im quite confused with how I can move materials between platforms. I have space platforms in my vulcanus science platform, and saved up some to quickly send to my new platform. I cant seem to get it to send it over