First, Oversold Cemetery has a triggered ability
603.1. Triggered abilities have a trigger condition and an effect. They are written as [Trigger condition], [effect], and begin with the word when, whenever, or at. They can also be expressed as [When/Whenever/At] [trigger event], [effect].
Second, assuming you only have 4 creatures in your graveyard, the following happens:two triggers go on the stack (assuming they have different targets)the first trigger resolves, pulling one creature out of your graveyardthen when the second trigger resolves, you have three creatures in your graveyard and do not get your second creature, as you fail to meet the condition of the intervening if clause
603.4. A triggered ability may read When/Whenever/At [trigger event], if [condition], [effect]. When the trigger event occurs, the ability checks whether the stated condition is true. The ability triggers only if it is; otherwise it does nothing. If the ability triggers, it checks the stated condition again as it resolves. If the condition isnt true at that time, the ability is removed from the stack and does nothing. Note that this mirrors the check for legal targets.