To get dried ice cream out of carpet you can use some liquid dish washing soap or hand washing soap and some water.
Mix the liquid dish washing soap or hand soap in some water and then use a scrub brush to dip into the water and soap and then scrub the dried ice cream out of the carpet.
The warm water and soap as well as the brush will help to soften the dried ice cream and help it come out of the carpet.
Then you can use a shop vac to suck the ice cream out of the carpet or use a carpet cleaning machine or upholstery cleaning machine to suck the dried ice cream out of the carpet.
You might also need to soak the dried ice cream stain in some warm water and soap for about 20 to 30 minutes and then use a carpet cleaning machine or upholstery cleaner.
Vinegar can also help lift the stain from the carpet.
But either way you will usually have to get down on the carpet and scrub the carpet.