Bottom row. On mine I have space left of centre and enter right of centre.
Its a full keyboard, you use the next two outwards on the bottom row to shift layers for access to all the punctuation. They actually very ergonomic. See olkb.com for more on the original.
This style of keyboard is called "40%" and, just as you would press shift+1 to input an exclamation mark, they're invariably set up with additional modifier keys (or chorded sequences) to input the values of all the missing keys.