We’re moving to a new farm without a barn (but there is a covered lean to attached to a garage). We’re bringing our 3 friendly barn cats and plan to keep them in the finished space above the garage before we let them loose. 

How long should we keep them inside so they know this is their new home?

I kept mine locked inside for a week before letting him out. :)

We moved from New Mexico to Texas with 5 horses, 7 ducks, 14 chickens, 2 dogs and 4 barn cats lol! I just let them out of their crates and they stuck around. They are friendly too so they know where the food comes from. 

I adopted some barn cats from a shelter. They had me keep them in a large kennel in the barn for a month before releasing. However, I think if the cats know you less time would be ok. 

Chandler brought home a barn cat to be a mouser at his shop, and he turned her out immediately.  She was friendly from the beginning and has never left the shop area.  (She's blessed us with 2 adorable kittens too!)  This may not be the norm tho.  

Awwwwww

Her name is (wait for it) Shoppy!!!!!   Her original owner didn't want her because she's very very friendly and would jump off hay bales onto your shoulders.  She drop kicked her one day when C and LB were her barn looking at a horse---he told her real quick if she didn't want her that he would take her.  (When Lula Bell went to get her, they had her shut up in a feed bag---who does that????)  Now when I feed her she climbs me and basically stands on her head on my shoulder---how anyone could be mean to that I don't understand.   

I'm a cat lover as well as any other animals, some people just dont have a heart, there would be no way I would put any animal in a sack, so heartless.. So glad Shoppy has found a great home with you guys, wish all animals were so lucky..Shoppy is such a funny name, LOL

Sometimes we aren't real original on naming.  His last shop cat I named George Strait, called him Strait.   Just cause he was a little gorgeous hunk of cat!!!