Firs, I'm so sorry to hear that you lost all of them in one night. When a mink or any of the others of the weasel family gain access, they will sometimes kill everything, even though they won't eat everything they kill. a weasel (or young mink) can squeeze through a quarter sized hole, so you must take care. if their head will fit through, so will the rest of their body. Pardon me...
Greetings and welcome to BYC! So glad you joined us, even if the reason for doing so is terrible. There's a wealth of info, knowledge and experience shared in the multitude of threads. Browse around and see what interesting stuff you can find. By all means post away when the desire strikes you, especially if you have questions (provide as much detail/info as possible and pictures truly help)... With all the great folks here, generally someone will respond in no time at all. Please make yourself at home!
You CAN make a predator proof coop and run for your (future) birds. The thing is, it isn't "cheep" and will take forethought and effort. I know you want to give your birds freedom and you CAN make a big enough run that they can get time out in the open... Their open will just be enclosed. There's a coop section with thousands of pictures and ideas and as I said before, many threads dealing specifically with predators.
A coop built on a concrete slab would prevent anything accessing your birds when they are inside. For the run area, you'll need to use 1/2" hardware cloth (wire - don't use 1/4" as it's "thinner" gauge wire and easier to break through). It should reach up the sides at least 2' You'll also need to put a skirt down around the outside to prevent diggers from going under the walls.
Oh, if you haven't done so already, PLEASE put at least your general location in your profile. It could be very important if/when you ask for or offer help or advice. You know, climate issues and such. Old folks like me will never remember from this thread. To add it, mouse hover over Account top right and a drop down will appear. Click on Personal Details and scan down. You'll see the spot for Location. Then go to the bottom and save changes. Thanks! Hope you enjoy the site!