I have always wanted to do that - how did you bring them up?
I started with a cheap clear plastic box from the likes of B&M. Maybe 18 x 12 inches, filled that with approx 6 inches of pond water.
I kept that inside the house.
The spawn was placed in there along with a good hand full of floating plants from the pond.
Being inside and warmer than the pond, they started to hatch in 2-3 weeks, rather than 3-4 weeks.
They lived off the "jelly" and their built in food source, for the first couple or so days ( 3 I think it was)
Once the jelly had gone, I microwaved small pieces of the plant leaves, in pond water, in a jar, until it was completely broken down,.
I stirred that and let it cool, ending up with slightly green water, to mimic the algae they would eat.
Be careful not to put too much in at a time. Sorry, I can't remember the quantities, but it become obvious if you are over feeding.
Coupled with this, I did water changes approx 50% every couple of days, or so. I kept a container of pond water inside,
to warm enough to match the tadpole "tank" water temp.
I kept this up until their legs started to show, not fully, but I watched for the buds.
Then I switched to buying frozen brine shrimp & blood worms from the local pet shop.
And continued to feed these, along with the algae water.
I reduced the water level a little and added a couple of small rocks that slightly broke the surface.
This can be anything, tree branch small log etc.
When their legs formed, due to it being a cold spring ( I had intended to release them all once that happened) I kept them inside, a bit longer.
I emptied some of the water, tilted the container so there was still a few inches of water, in about half, and added some moss ( garden centers or reptile shops, the latter being cheaper) just a small handful. not covering the entire dry end. at the dry end, keeping that moist, and leaving a small rock etc in the wet end just breaking the surface.
I continued to feed the brine brine shrimps & blood worms, ( but dropping the algae substitute) the latter in greater quantities.
These were always left to thaw in a jar, in pond water, from inside, and added to the wet end.
Once the outside temperatures warmed up for a couple of days, and no frosts predicted I released them back into the shallow end of the pond,
( I have a gradient at one end, covered in small pebbles, zero depth but moist, to slowly sloping into the pond.)
And don't forget to water change as the water will go stagnant, pretty quickly, being inside at room temperature.
I think that is everything, it was a few years ago now, but if I remember anything else, I'll update.