In most cases, you'll need to exile five cards named Dragon's Approach (the resolving one from the stack plus four more from your graveyard) to search for a Dragon card. However, if Dragon's Approach is a copy, you can still exile it along with four cards named Dragon's Approach from your graveyard to search for a Dragon card. The exiled copy will then cease to exist.

The last ability of Dragon's Approach lets you ignore the "four-of" rule. It doesn't let you ignore format legality. For example, during a Strixhaven Limited event, you can't add Dragon's Approach from your personal collection.