Hello
Miragod and welcome to Smogon!
Unfortunately, you do not have access to the character who checks IVs until you have finished the game. This means you have to calculate the IVs manually yourself if you're doing the story mode Latias. Thankfully, there are many IV calculators online. I recommend
MetalKid's IV Calculator as that is the most accurate in my opinion. The trick is to enter the base stats at level 30 in the first line, then apply EVs using Super Training and enter the new stats on the second line (make sure you enter the correct EVs alongside the stats). Repeat this several times until you get a definitive answer for each stat.
Here's a photo of me doing it for my Latias:
To save yourself time, only check the stats with the IV calculator if the stats in the summary screen look promising. For example, a Timid Latias with all perfect stats would be: (I use
this site to calculate these things)
HP: 97
Atk: 55
Def: 68
SpA: 80
SpD: 92
Spd: 88
Hope this help, and good luck with your soft resetting!