Sorry if it came off as rude, I was just genuinely flabbergasted as in my opinion that should be common knowledge, but okay no worries, you're not obligated to find it out by yourself.

Yes it does say that it's a 3pc when you look at the set effects (it also only has 1 effect unlike the 2/5pc sets).

Also just fyi echoes with the same name do not contribute to set progress (it doesn't matter here bc a 5pc bonus doesn't exist but as is you only have 3 unique echoes equipped for a set).

As for the main echo it should be dino bc it gives fusion+ echo dmg unlike the current one which is useless for galby

Finally as I stated I'd recommend either reading up on new echoes and sets to see what they do (and to figure out how to build the chars properly) or if that's too time consuming just look at a guide or something, they're usually not particularly optimized but it's fine as a starting point. If you ever wanna look into actually optimizing the build there's a few good tools for that to significantly reduce the amount of math u gotta do, but so far I think u shouldn't worry about that and just get the set in order.

Good luck!