Welcome to the forum hun! Sounds like you are doing your best to give your new betta a wonderful home! Hikari used to be the #1 food out there for bettas, I remember when I began keeping them about 10 years ago, everyone used Hikari Bio-Gold. Unfortunately Hikari changed the ingredients in their food in I believe it was 2010 and now Wheat Flour and Fish meal are now the top ingredients (Instead of the whole fish proteins it had before). The Bio-gold also contains monosodium glutamate (MSG), a flavour enhancer, which has been linked with all sorts of unwanted effects as a food additive. The new Bio-Gold has been linked to several cases of bloat and swim bladder issues in bettas.
Hikari is a very good food. Personally, I rank it third best, and third is NOT a bad number. PetCo keeps the Omega One Betta tablets (the ones I use) and NLS Betta pellets over in the actual fish food section, not the betta areas. It is entirely possible your store does not carry them at all, but check there next time you're in the area. The Omega Ones are the very first food on the top shelf from the left (I work at PetCo, so I have the fish food shelves about memorized). Its entirely possible your store didn't sell enough of them and they don't carry them, but that's where they would be if they do.
If they don't, Hikari is a very good food, and your betta will be quite healthy off it. I just don't use Hikari or NLS myself since they use Antarctic krill, and there are some serious overfishing problems of that krill that's leading to a decrease in the penguin population. Since penguins are the most superior animal in the world, I won't touch food with it.
I do have to say, I feed one out of the 3 pellets allotment to my Cambodian female CT Curious Grace. Within a week, her pectoral fins are showing some red strands in the fin rays that were never there before, she had fin regrowth from previous damage, and her red is brighter and more vibrant. My allotment: 1 of each NLS, OO, Hikari BG.
Im thinking of just alternating... Right now hes eating the bio-gold sporadically... he is devouring the micro wafers from Hikari... But they dont have the protein and fish content that the Bio-Gold has... He eats the bio gold then chews it a second or two then spits out half the pellet and re eats it lol... then goes and blows more buibbles for his bubble nest
Ok so I am a nut about feeding my pets... so in my travels today I found Omega One betta pellets and NLS betta pellets... So Lancelot will be dinning on a rotation of Hikari Bio-Gold pellets, Hikari Micro Wafer, Omega One Betta pellets and NLS betta pellets... I will either rotate them or feed a pellet of each twice a day... and add the wafers as a treat... So no worries Lancelot shall be eating like the King lol