Transplanting indoor birds nest
Overgrown 30” birds nest in shallow container
Certified GKH Gardening Expert
They look quite healthy. Transplanting can be pretty harsh on them too. Now will be the time to assess whether it will be best to sock them by moving them, or wait until they are showing signs of needing a transplant. Waiting will be best, to avoid unnecessary shock to a healthy plant.
Since they are epiphytes, and don't actually grow in soil in nature, you will have to treat them as such. An orchid mix is best, but a cactus mix can be ok, too. Knowing that they are epiphytic can help with their care. They are well suited for being rootbound. They won't mind a lack of rootspace, and can prefer it sometimes.
Should you choose to transplant, now... Just make sure to use an orchid or cactus mix. Don't separate the roots. Just put it into a slightly larger container, and bury it close to the same level as before.
Putting it into a container that is too large will likely lead to rot, and could potentially kill the plant.
Here is an article that will help you with the care of these plants: https://www.gardeningknowhow.com/houseplants/birds-nest-fern/birds-nest-fern-care.htm