Read Locations of three Gems in game Resident Evil 3 Remake.
Red Gem Location
You will find this item in donut shop. There is the door on the left. Move to the kitchen. There is a box with a Red Gem on the table. You unlock Hip Pouch upgrade.
Green Gem Location
There is the toy store on the right side of the street. Use a lock pick to open Yellow Padlock. Inside this store, you’ll find the box. Take the Green Gem. You will get Hand Grenade.
Blue Gem Location
Opposite the toy store there is another store. Use a bolt cutter to open this store. You’ll find a box with a Blue Gem on the desk. You unlock Tactical Stock for the Shotgun.
Once you insert all of the gems to unlock an achievement “Power Stones”.