Newbie transferring website / store to Squarespace site

I'm sure this has been discussed many times before! On my present website I create galleries of images from my photoshoots (usually password protected with sometimes many hundreds of images in each gallery) and then sell either prints of various sizes or image downloads (that I post or email out to the customer) I've built everything in Squarespace so far, but I'm struggling to see an easy way to replicate this particular commerce activity. You can visit my existing site here: https://www.studiograff-photo.co.uk/events to see how this works (this isn't password protected - Thurso High School prom). I've also screengrabbed the process in 4 sequential files below. ie click on the gallery thumbnail, choose an image, click "Buy now" and then select what print size, quality ect you want to purchase. I'm sure this can all be done in Squarespace, but I can't see that to do so far. Any advice or pointers would be most welcome. Thanks in advance