I'm trying to complete all the dex missions to get the Eevee emblem. but it says i've cleared them all. However, I only have 74 out of 100 Eevee Emblems. What am I missing?
74 out of 100 means you're missing 26 Eevee Grove emblem tickets, meaning it's very likely you're missing the Eevee and its Evolutions 2 themed collection, which rewards exactly 26 Eevee Grove emblem tickets when completed. This themed collection is the only collection or combination of collections that can reward 26 Eevee Grove emblem tickets, so assuming you have completed all the dex missions, this is the one you're missing.
Some of the quests in Themed Collections give out emblem tickets as a completion reward. Some of those even show Wonder Hourglasses as the displayed reward, but have a "..." icon at the top right; clicking on those collections will not only show what cards it takes to complete, but also displays the multiple types of rewards that exist for finishing the quest (not just the single type that appears in the list), which will include emblem tickets as well.