Study the Classics is a uncommon Sorcery card from Teenage Mutant Ninja Turtles Eternal (TMC), collector number 128. Current market price: $0.25, TCGplayer market prices via Scryfall.
Put a +1/+1 counter on target creature, then double the number of +1/+1 counters on it. You gain life equal to the number of +1/+1 counters on that creature.