I want to recreate a button

I am hoping to recreate this button that I designed another site but am in need of the code to do it on Squarespace. 

Also the same effect around photos (i.e. framing photos and creating the same shadow drop effect) 

Anyone able to help? 

That shouldn't be difficult with CSS, set a border and a drop shadow. You can use this button selector for the tertiary button style:

.sqs-button-element--tertiary