Hi and welcome to the forum
The easiest way to reduce ammonia, nitrite or nitrate is by doing a 75% water change and gavel cleaning the substrate every day until the levels are 0ppm. Then do it once or twice a week after that.
Make sure any new water is free of chlorine/ chloramine before it's added to the tank.
Reduce feeding to once every couple of days until the filters are able to deal with the ammonia and nitrite.
Did you change the filter media/ materials when you moved everything across to the bigger tank?
If yes, this is why you have ammonia in the water. You don't want to replace filter media unless it is falling apart. Filter media should be washed in a bucket of tank water, and the media is re-used. The bucket of dirty water gets poured on the lawn.
If filter media starts to break down/ fall apart, you can replace it with sponge from a different brand of filter. Use a pair of scissors to cut the sponge to fit. You clean sponges by washing in a bucket of tank water. Sponges last for years. You can add a sponge now if there is space in the filter and it will hold some bacteria if/ when you have to replace other filter media.