How to use

ReturnToHandFromGraveyardCost

in

mage.abilities.costs.common

@Override
public ReturnToHandFromGraveyardCost copy() {
  return new ReturnToHandFromGraveyardCost(this);
}

public ReturnToHandFromGraveyardCost(TargetCardInYourGraveyard target) {
  this.addTarget(target);
  if (target.getMaxNumberOfTargets() > 1 && target.getMaxNumberOfTargets() == target.getNumberOfTargets()) {
    this.text = new StringBuilder("return ").append(target.getMaxNumberOfTargets()).append(' ').append(target.getTargetName()).append(" from graveyard to it's owner's hand").toString();
  } else {
    this.text = new StringBuilder("return ").append(target.getTargetName()).append(" from graveyard to it's owner's hand").toString();
  }
}

public HarvestWurm(UUID ownerId, CardSetInfo setInfo) {
  super(ownerId,setInfo,new CardType[]{CardType.CREATURE},"{1}{G}");
  this.subtype.add(SubType.WURM);
  this.power = new MageInt(3);
  this.toughness = new MageInt(2);
  // When Harvest Wurm enters the battlefield, sacrifice it unless you return a basic land card from your graveyard to your hand.
  this.addAbility(new EntersBattlefieldTriggeredAbility(new SacrificeSourceUnlessPaysEffect(new ReturnToHandFromGraveyardCost(new TargetCardInYourGraveyard(StaticFilters.FILTER_CARD_BASIC_LAND)))));
}