Good Morning, Wachyvorlon,
Most professional labs will return the film in a strip from which the user can separate individual frames as desired. Some labs will put 6 x 6 transparencies in cardboard mounts, usually at an extra charge. Years ago, Kodak would routinely return 6 x 6 images in that manner. A lot of 120, of course is in other formats; in the larger ones (6 x 7, 6 x 9, 6 x 12, etc.) mounting is atypical, although it might be possible to find a lab which will do it. Mounting such images is usually pointless: a few people may have 6 x 7 projectors, but who has one for anything larger?
Konical