What fish are in your main tank? Are you planning on raising the babies? If so, I wouldn't put them in the main tank as they may become food. You could put them in a breeder net in the main tank, or just raise them in the little tank they are in. However, if you do want to move them into the large tank...how different are the water params in each tank? Basically, unless they are exactly even, you'll need to acclimate the fry slowly, as they can be sensitive to sudden changes.
My platies had fry in main tank and I found them in top of the filter box but as soon as I tried to get them they swam back into the tnk where the zebra danios were waiting for them
Others got ate during the night as they were popping out