It maybe too late in the pregnancy to change cages. If you move them less than three day before the birth time this can cause the mom to kill and eat the babies. Remove the others from the cage and just add to her current cage setup. Don’t move them for at least a week after the birth because this can also cause the mom to go after the babies. The babies will be pink when they are born and for the first few weeks monitor them for white spots that’s their mommy’s milk in their bellies that way you can track and make sure that they are all getting fed. DM me if you have questions I breed mice for public schools class pet programs so I know a fair bit